Optical phased array dynamic beam shaping with noise correction

ABSTRACT

A laser system including a seed laser, a laser beam splitting and combining subsystem receiving an output from the seed laser and providing a combined laser output having noise and a noise cancellation subsystem operative to provide a noise cancellation phase correction output based on taking into consideration the noise at intermittent times, the laser beam splitting and combining subsystem varying a phase of the combined laser output during time interstices between the intermittent times.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/IL2018/051184, filed Nov. 6, 2018, claiming priority to IsraelPatent Application No. 255496, entitled OPTICAL PHASED ARRAY DYNAMICBEAM SHAPING WITH NOISE CORRECTION, filed Nov. 7, 2017; to Israel PatentApplication No. 256107, entitled ‘ SEED LASER FAILURE PROTECTIONSYSTEM’, filed Dec. 4, 2017; to U.S. Provisional Patent Application Ser.No. 62/594,167, entitled ‘LASER BACK-REFLECTION PROTECTION USING OPTICALPHASED ARRAY LASER’, filed Dec. 4, 2017; to Israel Patent ApplicationNo. 258936, entitled ‘ SCALED PHASE MODIFICATION, PHASE CALIBRATION ANDSEED LASER PROTECTION IN OPTICAL PHASED ARRAY’, filed Apr. 25, 2018; toU.S. Provisional Patent Application No. 62/684,341, entitled ‘MULTIPLEDETECTORS AND CORRESPONDING MULTIPLE CLOSELY SPACED OPTICAL PATHWAYS INOPTICAL PHASED ARRAY LASER’, filed Jun. 13, 2018; and to U.S.Provisional Patent Application No. 62/702,957, entitled ‘DETECTOR MASKIN OPTICAL PHASED ARRAY LASER’, filed Jul. 25, 2018, the disclosures ofall of which are hereby incorporated by reference and priorities of allof which are hereby claimed pursuant to 37 CFR 1.78(a)(4) and (5)(i).

Reference is also made to U.S. Pat. No. 9,893,494, the disclosure ofwhich is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to laser coherent beam combiningand more particularly to optical phased arrays.

BACKGROUND OF THE INVENTION

Various types of optical phased arrays are known in the art.

SUMMARY OF THE INVENTION

The present invention seeks to provide systems and methods relating tonoise correction and phase modification in dynamically shaped beamsproduced by laser optical phased arrays.

There is thus provided in accordance with a preferred embodiment of thepresent invention a laser system including a seed laser, a laser beamsplitting and combining subsystem receiving an output from the seedlaser and providing a combined laser output having noise and a noisecancellation subsystem operative to provide a noise cancellation phasecorrection output based on taking into consideration the noise atintermittent times, the laser beam splitting and combining subsystemvarying a phase of the combined laser output during time intersticesbetween the intermittent times.

There is further provided in accordance with another preferredembodiment of the present invention a laser system including a seedlaser, a laser beam splitting and combining subsystem receiving anoutput from the seed laser and providing a combined laser output havingnoise and a noise cancellation subsystem operative to provide a noisecancellation phase correction output, based on taking into considerationthe noise at a noise sampling rate, the laser beam splitting andcombining subsystem varying a phase of the combined laser output at aphase varying rate which exceeds the noise sampling rate.

Preferably, at least one of the noise sampling rate and the phasevarying rate changes over time.

Preferably, the noise sampling rate is predetermined.

In accordance with a preferred embodiment of the present invention, thelaser beam splitting and combining subsystem varies a phase of thecombined laser output to provide spatial modulation of the combinedlaser output.

Preferably, the spatial modulation of the combined laser output isprovided in combination with mechanical spatial modulation of thecombined laser output, the spatial modulation in combination with themechanical spatial modulation being faster than the mechanical spatialmodulation in the absence of the spatial modulation.

Additionally or alternatively, the spatial modulation of the combinedlaser output is provided in combination with mechanical spatialmodulation of the combined laser output, the spatial modulation incombination with the mechanical spatial modulation being more precisethan the mechanical spatial modulation in the absence of the spatialmodulation.

Preferably, the spatial modulation includes modulation of at least oneof a shape and a diameter of the combined laser output.

Preferably, the laser beam splitting and combining subsystem provideslaser beam amplification downstream of the splitting and upstream of thecombining.

In accordance with a further preferred embodiment of the presentinvention, the noise cancellation phase correction output is calculatedbased on sequentially applying at least two phase changes to at leastone constituent beam of the combined laser output and identifying onephase change of the at least two phase changes corresponding to amaximum output intensity of the at least one constituent beam.

Preferably, the system also includes at least one detector cooperativelycoupled to the noise cancellation subsystem for detecting at least aportion of the combined laser output.

Preferably, the at least one detector performs the detectingcontinuously.

In accordance with an additionally preferred embodiment of the presentinvention, the noise cancellation phase correction output cancelsintensity noise in the combined laser output.

Preferably, the system also includes at least one intensity modulatorfor varying an intensity of the combined laser output.

In accordance with a still additionally preferred embodiment of thepresent invention, the noise cancellation phase correction outputcancels position noise in the combined laser output.

Preferably, the system also includes at least one position modulator forvarying a position of the combined laser output.

Preferably, a laser cutting system includes the laser system of thepresent invention.

Additionally or alternatively, a laser additive manufacturing systemincludes the laser system of the present invention.

Still additionally or alternatively, a laser welding system includes thelaser system of the present invention.

Further additionally or alternatively, a free-space opticalcommunication system includes the laser system of the present invention.

There is also provided in accordance with a preferred embodiment of thepresent invention a method for performing noise correction on a phasevaried laser output including receiving an output from a seed laser,splitting and combining the output to provide a combined laser outputhaving noise, applying a noise cancellation phase correction output tothe combined laser output based on taking into consideration the noiseat intermittent time, and varying a phase of the combined laser outputduring time interstices between the intermittent times.

There is further provided in accordance with another preferredembodiment of the present invention a method for performing noisecorrection on a phase varied laser output including receiving an outputfrom a seed laser, splitting and combining the output to provide acombined laser output having noise, applying a noise cancellation phasecorrection output to the combined laser output, based on taking intoconsideration the noise at a noise sampling rate, and varying a phase ofthe combined laser output at a phase varying rate which exceeds thenoise sampling rate.

Preferably, at least one of the noise sampling rate and the phasevarying rate changes over time.

Preferably, the noise sampling rate is predetermined.

In accordance with a preferred embodiment of the present invention, thevarying of the phase provides spatial modulation of the combined laseroutput.

Preferably, the spatial modulation of the combined laser output isprovided in combination with mechanical spatial modulation of thecombined laser output, the spatial modulation in combination with themechanical spatial modulation being faster than the mechanical spatialmodulation in the absence of the spatial modulation.

Additionally or alternatively, the spatial modulation of the combinedlaser output is provided in combination with mechanical spatialmodulation of the combined laser output, the spatial modulation incombination with the mechanical spatial modulation being more precisethan the mechanical spatial modulation in the absence of the spatialmodulation.

Preferably, the spatial modulation includes modulation of at least oneof a shape and a diameter of the combined laser output.

Preferably, the method also includes amplifying the output, downstreamof the splitting and upstream of the combining.

In accordance with another preferred embodiment of the presentinvention, the method also includes calculating the noise cancellationphase correction output based on sequentially applying at least twophase changes to at least one constituent beam of the combined laseroutput and identifying one phase change of the at least two phasechanges corresponding to a maximum output intensity of the at least oneconstituent beam.

Preferably, the method also includes detecting at least a portion of thecombined laser output.

Preferably, the detecting is performed continuously.

In accordance with yet another preferred embodiment of the presentinvention, the noise cancellation phase correction output cancelsintensity noise in the combined laser output.

Preferably, the method also includes modulating an intensity of theoutput, downstream of the splitting and upstream of the combining.

In accordance with still another preferred embodiment of the presentinvention, the noise cancellation phase correction output cancelsposition noise in the combined laser output.

Preferably, the method also includes modulating a position of theoutput, downstream of the splitting and upstream of the combining.

Preferably, a method for laser cutting includes the method of thepresent invention.

Additionally or alternatively, a method for additive manufacturingincludes the method of the present invention.

Further additionally or alternatively, a method for laser weldingincludes the method of the present invention.

Still further additionally or alternatively, a method for free spaceoptical communication includes the method of the present invention.

There is also provided in accordance with another preferred embodimentof the present invention a laser system including a seed laser, a laserbeam splitting and combining subsystem receiving an output from the seedlaser and providing a combined laser output, the laser beam splittingand combining subsystem varying a phase of the combined laser output, aplurality of detectors detecting the combined laser output atintermittent times during the varying of the phase of the combined laseroutput and a plurality of optical pathways between the combined laseroutput and the plurality of detectors for providing therealong thecombined laser output to the plurality of detectors, a spatial densityof the plurality of optical pathways being greater than a spatialdensity of the plurality of detectors.

Preferably, the combined laser output has noise and the laser systemalso includes a noise cancellation subsystem operative to provide anoise cancellation phase correction output based on taking intoconsideration the noise of the combined laser output, as detected by theplurality of detectors at the intermittent times during the varying ofthe phase of the combined laser output.

Preferably, the plurality of optical pathways includes a plurality ofoptical fibers, ends of the optical fibers being arranged with thespatial density greater than the spatial density of the plurality ofdetectors.

Preferably, ones the plurality of optical pathways are interspaced by adistance of 20-1000 microns.

Preferably, ones of the plurality of detectors are interspaced by adistance of 5-50 mm.

There is additionally provided in accordance with another preferredembodiment of the present invention method for detecting a laser outputincluding receiving an output from a seed laser, splitting and combiningthe output to provide a combined laser output, varying a phase of thecombined laser output and providing the combined laser output to aplurality of detectors along a plurality of optical pathways, a spatialdensity of the plurality of optical pathways being greater than aspatial density of the plurality of detectors.

Preferably, the combined laser output has noise and the method alsoincludes providing a noise cancellation phase correction output based ontaking into consideration the noise of the combined laser output, asdetected by the plurality of detectors during the varying of the phaseof the combined laser output.

Preferably, the plurality of optical pathways includes a plurality ofoptical fibers, ends of the optical fibers being arranged with thespatial density greater than the spatial density of the plurality ofdetectors.

Preferably, ones the plurality of optical pathways are interspaced by adistance of 20-1000 microns.

Preferably, ones of the plurality of detectors are interspaced by adistance of 5-50 mm.

There is further provided in accordance with yet another preferredembodiment of the present invention a laser system including a seedlaser, a laser beam splitting and combining subsystem receiving anoutput from the seed laser and providing a combined laser output, thelaser beam splitting and combining subsystem varying a phase of thecombined laser output, at least one detector detecting the combinedlaser output during the varying of the phase of the combined laseroutput and an optical mask including at least one of a transmissiveregion and a reflective region for respectively providing therethroughand therefrom the combined laser output to the at least one detector.

Preferably, at least one of the transmissive region and the reflectiveregion is configured in accordance with at least one of a shape and atrajectory of the combined laser output.

Preferably, the system also includes a focusing subsystem interfacingthe optical mask and the at least one detector for focusing the combinedlaser output onto the at least one detector.

Preferably, the focusing subsystem includes at least one focusing lens.

Preferably, the at least one detector includes a single detector.

In accordance with a preferred embodiment of the present invention, thetransmissive region has non-uniform transparency.

Preferably, the non-uniform transparency of the transmissive regioncompensates for non-noise related non-uniformity in intensity of thecombined laser output.

Preferably, the optical mask includes an electrically modulated deviceand the at least one of the transmissive region and the reflectiveregion is electronically modifiable.

Preferably, the optical mask includes an LCD screen.

In accordance with another preferred embodiment of the presentinvention, the reflective region has non-uniform reflectivity.

Preferably, the non-uniform reflectivity of the reflective regioncompensates for non-noise related non-uniformity in intensity of thecombined laser output.

Preferably, the reflective region includes a DMM.

Preferably, the combined laser output has noise and the laser systemalso includes a noise cancellation subsystem operative to provide anoise cancellation phase correction output based on taking intoconsideration the noise of the combined laser output, as detected by theat least one detector during the varying of the phase of the combinedlaser output.

There is still further provided in accordance with still a furtherpreferred embodiment of the present invention a method for detecting alaser output including receiving an output from a seed laser, splittingand combining the output to provide a combined laser output, varying aphase of the combined laser output, providing, by an optical mask, thecombined laser output to at least one detector, the optical maskincluding at least one of a transmissive region and a reflective regionfor respectively providing therethrough and therefrom the combined laseroutput to the at least one detector and detecting, by the at least onedetector, the combined laser output during the varying of the phase.

Preferably, the at least one of the transmissive region and thereflective region is configured in accordance with at least one of ashape and a trajectory of the combined laser output.

Preferably, the method also includes focusing the combined laser outputonto the at least one detector.

Preferably, the method also includes providing a focusing lensinterfacing the optical mask and the at least one detector, forperforming the focusing.

Preferably, the at least one detector includes a single detector.

In accordance with a preferred embodiment of the present invention, thetransmissive region has non-uniform transparency.

Preferably, the non-uniform transparency of the transmissive regioncompensates for non-noise related non-uniformity in intensity of thecombined laser output.

Preferably, the optical mask includes an electrically modulated deviceand the at least one of the transmissive region and the reflectiveregion is electronically modifiable.

Preferably, the optical mask includes an LCD screen.

In accordance with another preferred embodiment of the presentinvention, the reflective region has non-uniform reflectivity.

Preferably, the non-uniform reflectivity of the reflective regioncompensates for non-noise related non-uniformity in intensity of thecombined laser output.

Preferably, the reflective region includes a DMM.

Preferably, the combined laser output has noise and the method alsoincludes providing a noise cancellation phase correction output based ontaking into consideration the noise of the combined laser output, asdetected by the at least one detector during the varying of the phase ofthe combined laser output.

There is also provided in accordance with yet another preferredembodiment of the present invention a laser system including a seedlaser, a laser splitting and combining subsystem receiving an outputfrom the seed laser and combining the output to provide a combined laseroutput, a phase modulation subsystem for varying a phase of the combinedlaser output and a voltage-to-phase correlation subsystem forcorrelating a voltage applied to the phase modulation subsystem to aphase modulating output produced by the phase modulation subsystem andfor providing a voltage-to-phase correlation output useful incalibrating the phase modulation subsystem, the correlating beingperformed periodically during the varying of the phase.

Preferably, the phase modulation subsystem includes a plurality of phasemodulators.

Preferably, the voltage is applied to the plurality of phase modulatorsby a phase modulation control module.

Preferably, the voltage includes a voltage intended to produce a phaseshift of the combined laser output of 2π.

Preferably, the correlating includes measuring a change in intensity ofa far-field intensity pattern of the combined laser output followingapplication of the voltage and deriving a relationship between thevoltage and a phase shift corresponding to the change in intensity.

Preferably, the voltage is sequentially applied to ones of the pluralityof phase modulators.

Preferably, the correlating is performed at a slower rate than thevarying of the phase.

Preferably, the varying of the phase is performed at a rate of 1 milliontimes per second and the correlating is performed at a rate of once persecond.

There is additionally provided in accordance with an additionallypreferred embodiment of the present invention a method for performingphase calibration of a laser system including receiving an output from aseed laser, splitting and combining the output to provide a combinedlaser output, varying a phase of the combined laser output by a phasemodulation subsystem, periodically during the varying of the phase,applying a voltage to the phase modulation subsystem and correlating thevoltage to a phase modulating output produced by the phase modulationsubsystem and providing a voltage-to-phase correlation output useful incalibrating the phase modulation subsystem.

Preferably, the phase modulation subsystem includes a plurality of phasemodulators.

Preferably, applying the voltage is performed by a phase modulationcontrol module.

Preferably, the voltage includes a voltage intended to produce a phaseshift of the combined laser output of 2π.

Preferably, the correlating includes measuring a change in intensity ofa far-field intensity pattern of the combined laser output followingapplication of the voltage and deriving a relationship between thevoltage and a phase shift corresponding to the change in intensity.

Preferably, the method also includes sequentially applying the voltageto ones of the plurality of phase modulators.

Preferably, the correlating is performed at a slower rate than thevarying of the phase.

Preferably, the varying of the phase is performed at a rate of 1 milliontimes per second and the correlating is performed at a rate of once persecond.

There is also provided in accordance with another preferred embodimentof the present invention a laser system including a seed laser, a laserbeam splitting and combining subsystem receiving an output from the seedlaser, splitting the output into a plurality of sub-beams and providinga combined laser output including the plurality of sub-beams and a phasemodulation subsystem grouping at least a portion of ones of theplurality of sub beams into a multiplicity of groups of sub-beams, thephase modulation subsystem in parallel across the multiplicity of groupsof sub-beams, varying a phase of each sub-beam within each grouprelative to phases of other sub-beams within the group so as to vary aphase of each group, and varying the phase of each group relative tophases of other ones of the multiplicity of groups, thereby varying aphase of the combined laser output.

Preferably, the phase modulation subsystem includes at least onecylindrical lens for performing the grouping.

Alternatively, the phase modulation subsystem includes an array ofmirrors and corresponding focusing lenses for performing the grouping.

Preferably, the phase modulation subsystem includes a plurality of phasemodulators for varying the phases of the sub-beams.

Preferably, the phase modulation subsystem includes at least oneelectronic control module in operative control of the plurality of phasemodulators.

Preferably, the phase modulation subsystem includes a multiplicity ofdetectors corresponding to the multiplicity of groups, for detecting afar field intensity pattern of each of the multiplicity of groups.

In accordance with a preferred embodiment of the present invention, thesystem also includes a multiplicity of optical masks maskingcorresponding ones of the multiplicity of detectors, each optical maskincluding at least one of a transmissive region and a reflective regionfor respectively providing therethrough and therefrom the far fieldintensity pattern to the corresponding detector of the multiplicity ofdetectors.

Preferably, the multiplicity of detectors performs the detecting atleast partially mutually simultaneously.

Preferably, the phase modulation subsystem includes an additionalauxiliary detector for detecting a combined far field intensity patternof the multiplicity of groups.

Preferably, the phase modulation subsystem includes a multiplicity ofadditional phase modulators, each additional phase modulator beingcommon to all sub-beams within each the group for varying the phase ofeach group relative to phases of other ones of the multiplicity ofgroups.

Preferably, the phase modulation subsystem includes an additionalelectronic control module in operative control of the multiplicity ofadditional phase modulators.

In accordance with another preferred embodiment of the presentinvention, each detector of the multiplicity of detectors includes aplurality of detectors.

Preferably, the system also includes a plurality of optical pathwaysbetween the far field intensity pattern of each of the multiplicity ofgroups and each plurality of detectors for providing the far fieldintensity pattern therealong to the plurality of detectors, a spatialdensity of the plurality of optical pathways being greater than aspatial density of the plurality of detectors.

Preferably, the varying of the phase of the combined laser outputincludes maximizing an intensity of the combined laser output.

Preferably, the varying of the phase of the combined laser outputprovides spatial modulation of the combined laser output, withoutinvolving mechanical spatial modulation of the combined laser output.

Preferably, the laser beam splitting and combining subsystem provideslaser beam amplification downstream of the splitting and upstream of thecombining.

There is further provided in accordance with still another preferredembodiment of the present invention a method for performing phasevariation of a laser output including receiving a laser output from aseed laser, splitting the laser output into a plurality of sub-beams andcombining the plurality of sub-beams to provide a combined laser output,grouping at least a portion of ones of the plurality of sub-beams into amultiplicity of groups of sub-beams, in parallel across the multiplicityof groups of sub-beams, varying a phase of each sub-beam within eachgroup relative to phases of other sub-beams within the group so as tovary a phase of each group and varying the phase of each group relativeto phases of other ones of the multiplicity of groups, thereby varying aphase of the combined laser output.

Preferably, the grouping is performed by at least one cylindrical lens.

Alternatively, the grouping is performed by an array of mirrors andcorresponding focusing lenses.

Preferably, the varying of the phases of the sub-beams is performed by aplurality of phase modulators.

Preferably, the method also includes controlling the plurality of phasemodulators by at least one electronic control module.

Preferably, the method also includes detecting a far field intensitypattern of each of the multiplicity of groups, by a correspondingmultiplicity of detectors.

In accordance with a preferred embodiment of the present invention, themethod includes providing, by a multiplicity of optical masks, the farfield intensity pattern to corresponding ones of the multiplicity ofdetectors, each optical mask including at least one of a transmissiveregion and a reflective region for respectively providing therethroughand therefrom the far field intensity pattern to the correspondingdetector of the multiplicity of detectors.

Preferably, the detecting is performed at least partially mutuallysimultaneously for the multiplicity of groups.

Preferably, the method also includes detecting a combined far fieldintensity pattern of the multiplicity of groups, by an auxiliarydetector.

Preferably, the varying of the phase of each group relative to phases ofother ones of the multiplicity of groups is performed by a multiplicityof additional phase modulators, each additional phase modulator beingcommon to all sub-beams within each the group.

Preferably, the method also includes controlling the multiplicity ofadditional phase modulators by an additional electronic control module.

In accordance with another preferred embodiment of the presentinvention, each detector of the multiplicity of detectors includes aplurality of detectors.

Preferably, the method also includes providing the far field intensitypattern of each of the multiplicity of groups to each plurality ofdetectors along a plurality of optical pathways, a spatial density ofthe plurality of optical pathways being greater than a spatial densityof the plurality of detectors.

Preferably, the varying of the phase of the combined laser outputincludes maximizing an intensity of the combined laser output.

Preferably, the varying of the phase of the combined laser outputprovides spatial modulation of the combined laser output, withoutinvolving mechanical spatial modulation of the combined laser output.

Preferably, the method also includes amplifying the laser outputdownstream of the splitting and upstream of the combining.

There is still further provided in accordance with another preferredembodiment of the present invention a laser system including an opticalphased array laser including a seed laser and a laser beam splitting andcombining subsystem receiving a laser output from the seed laser andproviding a combined laser output, the laser beam splitting andcombining subsystem varying a phase of the combined laser output tofocus the combined laser output on a substrate, the combined laseroutput not being focused on the substrate in the absence of the varyingof the phase.

Preferably, the system also includes an optical element receiving thecombined laser output from the laser beam splitting and combiningsubsystem and focusing the combined laser output at a focal point notcoincident with the substrate.

Preferably, laser beams back-scattered from the substrate are notfocused on the optical phased array laser.

There is yet further provide in accordance with still another preferredembodiment of the present invention a method for focusing of laser beamsin a laser system including receiving a laser output from a seed laser,splitting and combining the laser output to provide a combined laseroutput and varying a phase of the combined laser output to focus thecombined laser output on a substrate, the combined laser output notbeing focused on the substrate in the absence of the varying of thephase.

Preferably, the method also includes focusing the combined laser output,by an optical element, at a focal point not coincident with thesubstrate.

Preferably, laser beams back-scattered from the substrate are notfocused on the laser system.

There is additionally provided in accordance with a still additionallypreferred embodiment of the present invention a laser amplifier systemincluding a seed laser providing a laser output, an amplifying subsystemreceiving the laser output from the seed laser along a first opticalpath and providing an amplified laser output and a detector subsystemreceiving the laser output from the seed laser along a second opticalpath, the detector subsystem being operative to deactivate theamplifying subsystem upon detection by the detector subsystem of atleast one fault in the laser output, a first time of flight of the laseroutput along the first optical path from the seed laser to theamplifying subsystem being greater than a combination of a second timeof flight of the laser output along the second optical path from theseed laser to the detector subsystem and a time taken for the detectorsubsystem to deactivate the amplifying subsystem.

Preferably, the first optical path includes a coiled optical fiber.

Preferably, the at least one fault includes at least one of reduction ofpower of the laser output and degradation of line width of the laseroutput.

Preferably, the amplifying subsystem includes a power amplifier and thelaser amplifier system includes a MOPA.

There is yet additionally provided in accordance with yet anadditionally preferred embodiment of the present invention a method forpreventing damage to an amplifying subsystem in a laser system includingreceiving a laser output from a seed laser along a first optical path,amplifying the laser output to provide an amplified laser output,receiving a laser output from the seed laser along a second opticalpath, detecting at least one fault in the laser output received alongthe second optical path and stopping the amplifying upon the detectingof the at least one fault in the laser output, a first time of flight ofthe laser output along the first optical path being greater than acombination of a second time of flight of the laser output along thesecond optical path and a time taken for the stopping of the amplifyingto be implemented.

Preferably, the first optical path includes a coiled optical fiber.

Preferably, the at least one fault includes at least one of reduction ofpower of the laser output and degradation of line width of the laseroutput.

Preferably, the amplifying subsystem includes a power amplifier and thelaser amplifier system includes a MOPA.

There is also provided in accordance with still another preferredembodiment of the present invention a laser amplifier system including aseed laser providing a laser output, a first amplifier arranged toreceive the laser output from the seed laser, the first amplifierproviding a first amplified laser output upon receipt of the laseroutput from the seed laser and providing one of amplified spontaneousemission and an additional laser output upon cessation of receipt of thelaser output from the seed laser and a second amplifier receiving one ofthe first amplified laser output, the amplified spontaneous emission andthe additional laser output from the first amplifier and providing asecond amplified laser output, amplification provided by the secondamplifier being greater than amplification provided by the firstamplifier.

Preferably, the system also includes a filter structure downstream ofthe seed laser and upstream of the first amplifier.

Preferably, the filter structure includes a beam splitter splitting thelaser output along a first and a second optical path, the first opticalpath being longer than the second optical path, a detector detecting acombined laser output from the first and second optical paths, anelectronic control module coupled to the detector, for receiving anoutput from the detector and a phase control module located along one ofthe first and second optical paths, the phase control module beingoperated by the electronic control module to modify a phase of the laseroutput responsive to detection by the detector of interference in thecombined laser output.

There is further provided in accordance with a still further preferredembodiment of the present invention a method for preventing damage to anamplifier in a laser system including receiving a laser output from aseed laser, providing, by a first amplifier, a first amplified laseroutput upon receipt of the laser output from the seed laser, providing,by the first amplifier, one of amplified spontaneous emission and anadditional laser output upon cessation of the receipt of the laseroutput from the seed laser and receiving, by a second amplifier, one ofthe first amplified laser output, the amplified spontaneous emission andthe additional laser output and providing a second amplified laseroutput, the second amplified laser output being greater than the firstamplified laser output.

Preferably, the method also includes filtering the laser outputdownstream from the seed laser and upstream from the first amplifier.

Preferably, the filtering includes splitting the laser output along afirst and a second optical path, the first optical path being longerthan the second optical path, detecting, by a detector, a combined laseroutput from the first and second optical paths, receiving, by anelectronic control module, an output from the detector and modifying aphase of the laser output along one of the first and second opticalpaths, responsive to detection by the detector of interference in thecombined laser output.

There is still further provided in accordance with another preferredembodiment of the present invention a laser amplifier system including aseed laser providing a first laser output having a first power, anamplifying subsystem receiving the first laser output from the seedlaser and providing an amplified laser output and an auxiliary lasersubsystem providing a second laser output at least upon cessation of thefirst laser output, the second laser output having a second power lowerthan the first power.

Preferably, the auxiliary laser subsystem includes an additional seedlaser providing the second laser output to the amplifying subsystem atleast concurrently with the providing of the first laser output.

Alternatively, the amplifying subsystem includes an entry at which thefirst laser output is received and an exit at which the amplified laseroutput is provided and the laser amplifier system includes a firstreflection grating positioned at the entry and a second reflectiongrating positioned at the exit, the first and second reflection gratingsin combination with the amplifying subsystem including the auxiliarylaser subsystem.

Preferably, the first and second reflection gratings are reflective in awavelength range of 1090 nm-1100 nm.

Preferably, the second laser output is of a different wavelength thanthe first laser output.

Preferably, the system also includes a filter downstream of the seedlaser and upstream of the amplifying subsystem.

Preferably, the filter includes a beam splitter splitting the firstlaser output along a first optical path and a second optical path, thefirst optical path being longer than the second optical path, a detectordetecting a combined laser output from the first and second opticalpaths, an electronic control module coupled to the detector, forreceiving an output from the detector and a phase control module locatedalong one of the first and second optical paths, the phase controlmodule being operated by the electronic control module to modify a phaseof the first laser output responsive to detection by the detector ofinterference in the combined laser output.

Preferably, the system also includes a detector subsystem for detectingthe first laser output from the seed laser.

Preferably, the detector subsystem includes a splitter splitting thefirst laser output into a first portion and a second portion, anadditional amplifier amplifying the second portion and providing anamplified output and an optical fiber receiving the amplified output,the optical fiber being configured to exhibit non-linear effects upon aline width of the first laser output becoming unacceptably narrow.

Preferably, the optical fiber has a length of 25 m and a core diameterof 6 microns.

There is yet additionally provided in accordance with another preferredembodiment of the present invention a method for preventing damage to anamplifier in a laser system including providing a first laser outputhaving a first power, amplifying the first laser output by an amplifier,to provide an amplified laser output and providing a second laser outputat least upon cessation of the providing of the first laser output, thesecond laser output having a second power lower than the first power.

Preferably, the providing of the second laser output is performed atleast concurrently with the providing of the first laser output.

Preferably, the amplifier includes an entry at which the first laseroutput is received and an exit at which the amplified laser output isprovided, and also including positioning a first reflection grating atthe entry and a second reflection grating at the exit, the first andsecond reflection gratings in combination with the amplifier providingthe second laser output.

Preferably, the first and second reflection gratings are reflective in awavelength range of 1090 nm-1100 nm.

Preferably, the second laser output is of a different wavelength thanthe first laser output.

Preferably, the method also includes filtering the first laser outputupstream of the amplifying of the first laser output.

Preferably, the method includes splitting the first laser output along afirst and a second optical path, the first optical path being longerthan the second optical path, detecting by a detector a combined laseroutput from the first and second optical paths, receiving, by anelectronic control module, an output from the detector and modifying aphase of the first laser output along one of the first and secondoptical paths, based on the output from the detector and responsive todetection by the detector of interference in the combined laser output.

Preferably, the method also includes detecting the first laser output.

Preferably, the detecting includes splitting the first laser output intoa first portion and a second portion, amplifying the second portion andproviding an amplified output and receiving the amplified output by anoptical fiber, the optical fiber being configured to exhibit non-lineareffects upon a line width of the first laser output becomingunacceptably narrow.

Preferably, the optical fiber has a length of 25 m and a core diameterof 6 microns.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fullybased on the following detailed description taken in conjunction withthe drawings in which:

FIG. 1A is a simplified schematic illustration of an optical phasedarray laser system for noise corrected dynamic beam shaping, constructedand operative in accordance with a preferred embodiment of the presentinvention;

FIGS. 1B and 1C are simplified graphical representations of phasevariation and noise correction in a system of the type illustrated inFIG. 1A;

FIG. 2A is a simplified schematic illustration of an optical phasedarray laser system for noise corrected dynamic beam shaping, constructedand operative in accordance with another preferred embodiment of thepresent invention;

FIGS. 2B and 2C are simplified graphical representations of phasevariation and noise correction in a system of the type illustrated inFIG. 2A;

FIG. 3A is a simplified schematic illustration of an optical phasedarray laser system for noise corrected dynamic beam shaping, constructedand operative in accordance with a further preferred embodiment of thepresent invention;

FIGS. 3B and 3C are simplified graphical representations of phasevariation and noise correction in a system of the type illustrated inFIG. 3A;

FIG. 4A is a simplified schematic illustration of an optical phasedarray laser system for noise corrected dynamic beam shaping, constructedand operative in accordance with a still further preferred embodiment ofthe present invention;

FIGS. 4B and 4C are simplified graphical representations of phasevariation and noise correction in a system of the type illustrated inFIG. 4A;

FIGS. 5A-5G are simplified illustrations of possible far-field motion ofan output of an optical phased array laser system of any of the typesillustrated in FIGS. 1A-4C;

FIG. 6 is a simplified schematic illustration of an optical phased arraylaser system including multiple detectors and corresponding multipleclosely spaced optical pathways, constructed and operative in accordancewith yet another preferred embodiment of the present invention;

FIG. 7 is a simplified schematic illustration of an optical phased arraylaser system including multiple detectors and corresponding multipleclosely spaced optical pathways, constructed and operative in accordancewith still another preferred embodiment of the present invention;

FIG. 8 is a simplified schematic illustration of an optical phased arraylaser system including multiple detectors and corresponding multipleclosely spaced optical pathways, constructed and operative in accordancewith yet a further preferred embodiment of the present invention;

FIG. 9 is a simplified schematic illustration of an optical phased arraylaser system including a detector mask configured in accordance with anexemplary laser beam trajectory, constructed and operative in accordancewith a preferred embodiment of the present invention;

FIG. 10 is a simplified schematic illustration of a detector mask of thetype illustrated in FIG. 9 showing varying levels of transparencythereof;

FIG. 11 is a simplified schematic illustration of an optical phasedarray laser system including a detector mask configured in accordancewith an exemplary laser beam shape, constructed and operative inaccordance with another preferred embodiment of the present invention;

FIG. 12 is a simplified schematic illustration of a detector mask of thetype illustrated in FIG. 11 , showing varying levels of transparencythereof;

FIG. 13 is a simplified schematic illustration of an optical phasedarray laser system including voltage-phase correlating functionality,constructed and operative in accordance with a preferred embodiment ofthe present invention;

FIG. 14 is a simplified flow chart illustrating steps for performingvoltage-phase correlation in a system of the type illustrated in FIG. 13;

FIG. 15 is a simplified schematic plan view illustration of an opticalphased array laser system including scaled phase modification of dynamicbeams, constructed and operative in accordance with an additionalpreferred embodiment of the present invention;

FIG. 16 is a simplified schematic plan view illustration of an opticalphased array laser system including scaled phase modification of dynamicbeams, constructed and operative in accordance with yet an additionalpreferred embodiment of the present invention;

FIGS. 17A and 17B are simplified top and perspective views of an opticalphased array laser system including scaled phase modification of dynamicbeams of a type illustrated in FIG. 15 or FIG. 16 ;

FIG. 18 is a simplified schematic plan view illustration of an opticalphased array laser system including scaled phase modification of dynamicbeams, constructed and operative in accordance with a further preferredembodiment of the present invention;

FIG. 19 is a simplified schematic plan view illustration of an opticalphased array laser system including scaled phase modification of dynamicbeams, constructed and operative in accordance with yet a furtherpreferred embodiment of the present invention;

FIGS. 20A and 20B are simplified top and perspective views of an opticalphased array laser system including scaled phase modification of dynamicbeams of a type illustrated in FIG. 18 or FIG. 19 ;

FIG. 21 is a simplified schematic plan view illustration of an opticalphased array laser system including scaled phase modification of dynamicbeams, constructed and operative in accordance with a still furtherpreferred embodiment of the present invention;

FIGS. 22A and 22B are simplified schematic illustrations of respectivefirst and second focal states of an optical phased array laser systemconstructed and operative in accordance with a preferred embodiment ofthe present invention;

FIG. 23 is a simplified representation of back-scatter in an opticalphased array laser system of the type illustrated in FIGS. 22A and 22B;

FIG. 24 is a simplified schematic diagram of a laser amplifying systemincluding a seed laser failure protection system constructed andoperative in accordance with a preferred embodiment of the presentinvention;

FIG. 25 is a simplified schematic diagram of a laser amplifying systemincluding a seed laser failure protection system constructed andoperative in accordance with another preferred embodiment of the presentinvention;

FIG. 26 is a simplified schematic diagram of a laser amplifying systemincluding a seed laser failure protection system constructed andoperative in accordance with a further preferred embodiment of thepresent invention;

FIG. 27 is a simplified schematic diagram of a laser amplifying systemincluding a seed laser failure protection system constructed andoperative in accordance with yet another preferred embodiment of thepresent invention;

FIG. 28 is a simplified schematic diagram of a laser amplifying systemincluding a seed laser failure protection system constructed andoperative in accordance with still another preferred embodiment of thepresent invention;

FIG. 29 is a simplified schematic illustration of a laser amplificationsystem including a seed laser failure protection system constructed andoperative in accordance with yet a further preferred embodiment of thepresent invention;

FIG. 30 is a simplified schematic illustration of a laser amplificationsystem including a seed laser failure protection system constructed andoperative in accordance with a still further preferred embodiment of thepresent invention;

FIG. 31 is a simplified schematic illustration of a laser amplificationsystem including a seed laser failure protection system constructed andoperative in accordance with yet an additional preferred embodiment ofthe present invention;

FIG. 32 is a simplified schematic illustration of a laser amplificationsystem including a seed laser failure protection system constructed andoperative in accordance with a still additional preferred embodiment ofthe present invention; and

FIG. 33 is a simplified schematic illustration of a sensor useful in alaser amplification system of any of the types illustrated in FIGS.24-32 .

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1A, which is a simplified schematicillustration of an optical phased array laser system for noise correcteddynamic beam shaping, constructed and operative in accordance with apreferred embodiment of the present invention; and to FIGS. 1B and 1C,which are simplified graphical representations of phase variation andnoise correction in a system of the type illustrated in FIG. 1A.

As seen in FIG. 1A, there is provided an optical phased array (OPA)laser system 100, here shown to be employed, by way of example, within alaser cutting system 102. Laser cutting system 102 may include OPA lasersystem 100 mounted in spaced relation to a multi-axis positioning table104, upon which table 104 an item, such as an item 106, may be cut usinglaser system 100, as is detailed henceforth. It is understood thatalthough laser cutting system 102 is illustrated herein in the contextof table 104, system 102 may be embodied as any type of laser cuttingsystem, as will be appreciated by one skilled in the art

As best seen at an enlargement 110, OPA laser 100 preferably comprises aseed laser 112 and a laser beam splitting and combining subsystem 114.Splitting and combining subsystem 114 preferably receives an outputlaser beam from seed laser 112 and splits the output laser beam into aplurality of sub-beams along a corresponding plurality of channels 116.Here, by way of example only, an output from seed laser 112 is shown tobe split into ten sub-beams along ten channels 116 although it isappreciated that splitting and combining subsystem 114 may include afewer or greater number of channels along which the output of seed laser112 is split, and typically may include a far greater number of channelssuch as 32 or more channels.

The relative phase of each sub-beam may be individually modulated by aphase modulator 118, preferably located along each of channels 116. Eachphase modulated sub-beam produced by the splitting and subsequent phasemodulation of the output of seed laser 112 preferably propagates towardsa collimating lens 119. The individually collimated, phase modulatedsub-beams are subsequently combined, for example at a focal lens 120, toform an output beam 122.

Splitting and combining subsystem 114 may also provide laseramplification of the sub-beams, preferably following the splitting ofthe output beam of seed laser 112 into sub-beams and prior to thecombining of the sub-beams to form output beam 122. Here, by way ofexample, splitting and combining subsystem 114 is shown to include aplurality of optical amplifiers 124 located along corresponding ones ofchannels 116 for amplifying each sub-beam. It is appreciated, however,that such amplification is optional and may be omitted, depending on thepower output requirements of OPA laser 100.

The phase of output beam 122, and hence the position and shape of thefar-field intensity pattern thereof, is controlled, at least in part, bythe relative phases of the constituent sub-beams combined to form outputbeam 122. In many applications, such as laser cutting as illustrated inFIG. 1A, it is desirable to dynamically move and shape the far-fieldintensity pattern of the output beam. This may be achieved in lasersystem 100 by laser splitting and combining subsystem 114 dynamicallyvarying the relative phases of the individual sub-beams and therebyvarying the phase of the combined laser output 122 so as dynamically tocontrol the position and shape of the far-field intensity patternthereof.

The relative phases of the sub-beams are preferably predetermined inaccordance with the desired laser output pattern for the cutting of item106. Particularly preferably, the varying relative phases are applied bya phase control subsystem 130. Phase control subsystem 130 preferablyforms a part of a control electronics module 132 in OPA laser 100 andpreferably controls each phase modulator 118 so as to dynamicallymodulate the relative phases of the sub-beams along channels 116.

Due to noise inherent in OPA system 100, output beam 122 has noise.Noise in output beam 122 is typically phase noise created by thermal ormechanical effects and/or by the amplification process in the case thatoptical amplifiers 124 are present in OPA system 100. It is a particularfeature of a preferred embodiment of the present invention that lasersystem 100 includes a noise cancellation subsystem 140 operative toprovide a noise cancellation phase correction output in order to cancelout the noise in output beam 122 in a manner detailed henceforth.

Particularly preferably, noise cancellation subsystem 140 employs analgorithm to sense and correct phase noise in the combined laser output.The noise cancellation phase correction output is preferably provided bynoise cancellation subsystem 140 to phase modulator 118 so as to correctphase noise in output beam 122 and thus avoid distortion of the shapeand position of the far field intensity pattern of output beam 122 thatwould otherwise be caused by the noise. Noise cancellation subsystem 140may be included in control electronics module 132.

It is understood that output beam 122 may be additionally oralternatively affected by types of noise other than phase noise,including intensity noise. In the case of output beam 122 havingintensity noise, noise cancellation subsystem 140 may be operative toprovide a noise cancellation phase correction output in order to cancelout the intensity noise in output beam 122. In such a case, OPA lasersystem 100 may optionally additionally include intensity modulators 142along channels 116 for modulating the intensity of each of the sub-beamsalong channels 116.

It is understood that output beam 122 may be additionally oralternatively affected by mechanical noise which may affect the relativeposition of the sub-beams. In the case of output beam 122 havingposition noise, noise cancellation subsystem 140 may be operative toprovide a noise cancellation phase correction output in order to cancelout the position noise in output beam 122. In such a case, OPA lasersystem 100 may optionally additionally include position modulators 144along channels 116 for modulating the position of each of the sub-beamsalong channels 116.

In order to facilitate application of phase variation and noisecorrection to output beam 122, a portion of the output of OPA laser 100is preferably extracted and directed towards at least one detector, hereillustrated as a single detector 150. Detector 150 may alternatively beembodied as multiple detectors, as detailed henceforth with reference toFIGS. 6-8 and 15-21 . The extracted portion of the output beampreferably functions as a reference beam, based on characteristics ofwhich the required noise correction and/or phase variation may becalculated. In the embodiment shown in FIG. 1A, plurality of sub-beamsalong channels 116 are directed towards a beam splitter 160. Beamsplitter 160 preferably splits each sub-beam into a transmitted portion162 and a reflected portion 164 in accordance with a predeterminedratio. For example, beam splitter 160 may split each sub-beam with a99.9% transmitted: 0.01% reflected ratio.

The transmitted portion 162 of the sub-beams preferably propagatestowards focal lens 120, at which focal lens 120 the sub-beams arecombined to form output beam 122 having a far-field intensity pattern166 incident on a surface of item 106. The reflected portion 164 of thesub-beams is preferably reflected towards an additional focal lens 168,at which additional focal lens 168 the sub-beams are combined to form anoutput reference beam 170 having a far-field intensity pattern 172incident on a surface of detector 150.

It is understood that the particular structure and configuration of beamsplitting and recombining elements shown herein, including beam splitter160 and focal lenses 120 and 168, is exemplary only and depicted in ahighly simplified form. It is appreciated that OPA laser system 100 mayinclude a variety of such elements, as well as additional opticalelements, including, by way of example only, additional or alternativelenses, optical fibers and coherent free-space far-field combiners.

As described hereinabove, the shape and position of far-field intensitypattern 166 of the output beam 122 and correspondingly of far-fieldintensity pattern 172 of the reference beam 170 are constantly changing,due to the ongoing variation of the relative phases of the sub-beams. Asa result, far-field intensity pattern 172 is not fixed upon detector 150but rather is constantly being moved around with respect to detector 150depending on the combined relative phases of the constituent sub-beams.However, in order for detector 150 to provide the required noisecancellation phase correction output, far-field intensity pattern 172must be incident upon detector 150 in order for detector to measure theintensity of far-field intensity pattern 172 and hence apply a noisecorrection accordingly, resulting in a fixed output beam.

The conflict between the dynamic nature of far-field intensity pattern172 due to the phase-variation thereof and the fixed nature required offar-field intensity pattern 172 in order to derive and apply noisecorrection thereto, is advantageously resolved in the present inventionby providing the noise cancellation and phase variation at mutuallydifferent times and rates.

The noise cancellation phase correction output is provided based ontaking into consideration noise measured at detector 150 at a noisesampling rate. The output beam 122 is controlled in such a way that thefar-field intensity pattern 172 is incident upon detector 150 during thecourse of the dynamic changes to the shape and position of output andreference far-field intensity patterns 166, 172 at a rate that is equalto or higher than the required noise sampling rate. The noise inreference beam 170 is taken into consideration during those intermittenttimes at which the far-field intensity pattern 172 is returned todetector 150.

At time interstices between the intermittent times at which far-fieldintensity pattern 172 is incident upon detector 150, the phase of thecombined output beams 122 and 170 is varied in order to dynamicallychange the shape and position of the far-field intensity pattern thereofas required to perform laser cutting of item 106. The combined laseroutput is varied at a phase varying rate which exceeds the noisesampling rate, in order to rapidly change the phase and hence shape andposition of the far-field intensity pattern. By way of example, thenoise sampling rate may be of the order of 10-1000 Hz whereas the phasevarying rate may be greater than 10,000 Hz.

The different rates and time scales over which the noise cancellationand phase variation are preferably performed in embodiments of thepresent invention may be best understood with reference to a graph 180seen in FIG. 1A and an enlarged version thereof shown in FIG. 1B.

As seen most clearly in FIG. 1B, graph 180 includes an upper portion 182displaying variation in intensity over time of far-field intensitypattern 172 as measured at detector 150 and a lower portion 184,displaying variation over the same time period of the relative phases ofa number of sub-beams contributing to output beam 122 and reference beam170. For the sake of simplicity, the relative phases of ten sub-beamsare displayed in graph 180, although it is appreciated that OPA system100 and hence the explanation provided herein is applicable to a feweror, more typically, a far greater number of sub-beams.

As seen in upper portion 182, intensity peaks 186 represent measuredintensity of the reference beam 170 when the far field intensity pattern172 passes over detector 150. As seen in lower portion 184, intensitypeaks 186 occur at intermittent times T_(i) at which the relative phaseof each sub-beam is zero, meaning that there is no shift in phasebetween the sub-beams, the position of the combined output beam istherefore not being changed and the far field intensity pattern 172 ishence directly incident on the detector 150. It is understood thatdetector 150 may alternatively be positioned such that the relativephase of the sub-beams thereat is non-zero. Furthermore, more than asingle detector may be employed so as to allow measurement of the farfield intensity pattern 172 at more than one location therealong, asdetailed henceforth with reference to FIGS. 6-8 and 15-21 .

Between intensity peaks 186 the measured intensity is close to zero, asthe far-field intensity pattern 172 is moved to the either side ofdetector 150 and thus is not directly incident on the detector 150. Asappreciated from consideration of upper portion 182, the magnitude ofintensity peaks 186 is not constant due to the presence of noise in thelaser output beam, which noise degrades the far field intensity pattern172.

As seen in lower portion 184, the relative phases of the sub-beams arevaried at time interstices T_(between) between intermittent times T_(i).In the phase variation function illustrated herein, the relative phasesof the sub-beams are shown to be varied in a periodic, regularlyrepeating pattern, with equal phase shifts being applied in the positiveand negative directions. It is appreciated that such a simplisticpattern is illustrative only and that the phase variation is notnecessarily regularly repeating, nor necessarily symmetrical in positiveand negative directions. Furthermore, it is understood that timeinterstices T_(between) preferably but not necessarily do not overlapwith intermittent times T_(i). Additionally, it is appreciated that atleast one of the phase varying rate and the noise sampling rate may beconstant or may change over time.

Noise cancellation subsystem 140 preferably operates by taking intoconsideration the noise at intermittent times T_(i) and providing anoise cancellation phase correction output based on the noise sensed atintermittent times T_(i). Noise cancellation subsystem 140 preferablyemploys an algorithm in order to sense noise and correct for the sensednoise accordingly.

According to one exemplary embodiment of the present invention, noisecancellation subsystem 140 employs an algorithm in which the relativephase of one channel is changed in such a way that the relative phase ismodified by a given phase change Δφ during each cycle of travel of thefar-field intensity pattern 172 with respect to detector 150. Followinga number of such cycles, in which a different phase change Δφ is appliedto the selected sub-beam over each cycle, the algorithm ascertains themaximum output intensity over all of the cycles and finds the optimumphase change Δφ that produced this maximum intensity. The phase changeof the selected sub-beam is then fixed at the optimum phase change Δφfor subsequent cycles and the algorithm proceeds to optimize anothersub-beam.

Graph 180 illustrates noise cancellation according to this exemplaryalgorithm in three sub-beams or channels A, B and C of the total of 10sub-beams. Sub-beams A, B and C are displayed alone in FIG. 1C for thesake of clarity. It is appreciated that the line style of the tracesrepresenting phase variation and noise correction of sub-beams A, B andC respectively is modified in FIG. 1C in comparison to FIGS. 1A and 1B,in order to aid differentiation between the various sub-beams for thepurposes of the explanation hereinbelow.

As seen initially in the case of channel A, and appreciated most clearlyfrom consideration of an enlargement 190, the dashed trace representsthe pattern of variation in relative phase of sub-beam A, as would beapplied by phase control sub-system 130 in the absence of any noisecorrection. This trace may be termed A_(uncorrected). The dotted- anddashed trace represents the actual relative phase of sub-beam A asmodified by the noise correction algorithm in order to find the optimumphase noise correction. This trace may be termed A_(corrected). Themodified relative phase of A_(corrected) is shifted with respect to thenon-modified relative phase of A_(uncorrected) by a different Δφ_(A)over the first five cycles of sub-beam A. The intensity 186 measured atdetector 150 varies over the first five cycles of optimization ofsub-beam A due to the deliberate change in relative phase shift.

Following the first five cycles of sub-beam A, the algorithm ascertainsthe maximum intensity and finds the phase change Δφ_(A) that producesthe maximum intensity. In this case, the maximum intensity is seen to beIA_(max) produced by the second phase shift Δφ_(A). The phase changeapplied to relative phase variation of sub-beam A is thus fixed at thesecond phase shift Δφ_(A) for subsequent cycles and the algorithmproceeds to optimize sub-beam B.

It is appreciated that during the sequential cycles of optimization ofsub-beam A, the relative phases of the remainder of the sub-beams arevaried as usual, each at a phase varying rate that far exceeds the noisesampling rate at which the noise in sub-beam A is taken intoconsideration.

As seen further in the case of sub-beam B, and appreciated most clearlyfrom consideration of an enlargement 192, the thicker trace duringoptimization of channel B represents the pattern of variation inrelative phase of sub-beam B, as would be applied by phase controlsub-system 130 in the absence of any noise correction. This trace may betermed B_(uncorrected). The thinner trace during optimization of channelB represents the actual relative phase of sub-beam B as modified by thenoise correction algorithm in order to find the optimum phase noisecorrection. This trace may be termed B_(corrected). The modifiedrelative phase of B_(corrected) is shifted with respect to thenon-modified relative phase of B_(uncorrected) by a different Δφ_(B)over five cycles of optimization sub-beam B. The intensity 186 measuredat detector 150 varies over these five cycles of optimization sub-beam Bdue to the deliberate change in relative phase shift.

Following these five cycles of sub-beam B, the algorithm ascertains themaximum intensity and finds the phase change Δφ_(B) that produces themaximum intensity. In this case, the maximum intensity is seen to beIAB_(max) produced by the fourth phase shift Δφ_(B). The phase changeapplied to relative phase variation of sub-beam B is then fixed at thefourth phase shift Δφ_(B) for subsequent cycles and the algorithmproceeds to optimize sub-beam C.

It is appreciated that during the five cycles of optimization ofsub-beam B, the relative phases of the remainder of the sub-beams arevaried as usual, each at a phase varying rate that far exceeds the noisesampling rate at which the noise in sub-beam B is taken intoconsideration.

A similar optimization process is preferably implemented for sub-beam C,in which a phase change Δφ_(C) is applied over several cycles in orderto optimize the output beam intensity and correct for intensitydegradation thereof due to phase noise in sub-beam C.

At least one detector 150 may operate continuously in order tocontinuously optimize the relative phases of the sub-beams and correctfor phase noise therein. However, due to a finite response time ofdetector 150, detector 150 only takes into consideration the noise inreference beam 170 at intermittent times, at a relatively slow noisesampling rate. The noise sampling rate is preferably but not necessarilypredetermined. The noise sampling rate may alternatively be random.

It is appreciated that the particular parameters of the noise correctionalgorithm depicted in graph 180 are exemplary only and may be readilymodified, as will be understood by one skilled in the art. For example,the phase shift Δφ may be optimized over a greater or fewer number ofcycles than illustrated herein, each sub-beam may be fully optimizedeach time the sub-beam passes over detector 150 or several sub-beams orall of the sub-beams may be optimized during each cycle in which thefar-field intensity pattern passes over detector 150. Furthermore,non-sequential noise correction optimization algorithms mayalternatively be implemented, including, but not limited to, Stochasticparallel gradient descent optimization algorithms.

The use of dynamically shaped, noise corrected optical phased arrayoutput beams for laser cutting is highly advantageous and enables rapidbeam steering, fast power modulation, fast beam focusing and beam shapetailoring. Both the speed and quality with which a material may be cutare improved using dynamically shaped, noise corrected optical phasearray output in comparison to conventional laser cutting methods. It isappreciated that but for the provision of noise correction, inaccordance with preferred embodiments of the present invention, theshape and position of the optical phased array output beam would bedegraded, thereby degrading the quality, speed and precision of thelaser cutting process.

In order to maintain output beam intensity as the far-field intensitypattern of the beam moves, as is advantageous in certain laser cuttingapplications, movement of the output beam may be controlled such thatthe beam spends more time at lower-intensity positions so as tocompensate for reduced power delivery thereat. Additionally oralternatively, an intensity profile mask such as a neutral density (ND)filter may be applied to the output beam in order to modify theintensity thereof.

Reference is now made to FIG. 2A, which is a simplified schematicillustration of an optical phased array laser system for noise correcteddynamic beam shaping, constructed and operative in accordance withanother preferred embodiment of the present invention; and to FIGS. 2Band 2C, which are simplified graphical representations of phasevariation and noise correction in a system of the type illustrated inFIG. 2A.

As seen in FIG. 2A, there is provided an optical phased array (OPA)laser system 200, here shown to be employed, by way of example, withinan additive manufacturing system 202. Additive manufacturing system 202may include OPA laser system 200 mounted in spaced relation to ascanning mirror 203 and multi-axis positioning table 204, upon whichtable 204 an item, such as an item 206, may be additively manufacturedusing laser system 200. It is understood that although additivemanufacturing system 202 is illustrated herein in the context ofscanning mirror 203, system 202 may be embodied as any type of additivemanufacturing system, as will be appreciated by one skilled in the art.

As best seen at an enlargement 210, OPA laser 200 preferably comprises aseed laser 212 and a laser beam splitting and combining subsystem 214.Splitting and combining subsystem 214 preferably receives an outputlaser beam from seed laser 212 and splits the output laser beam into aplurality of sub-beams along a corresponding plurality of channels 216.Here, by way of example only, an output from seed laser 212 is shown tobe split into ten sub-beams along ten channels 216 although it isappreciated that splitting and combining subsystem 214 may include afewer or greater number of channels along which the output of seed laser212 is split, and typically may include a far greater number of channelssuch as 32 or more channels.

The relative phase of each sub-beam may be individually modulated by aphase modulator 218, preferably located along each of channels 216. Eachphase modulated sub-beam produced by the splitting and subsequent phasemodulation of the output of seed laser 212 preferably propagates towardsa collimating lens 219. The individually collimated, phase modulatedsub-beams are subsequently combined, for example at a focal lens 220, toform an output beam 222.

Splitting and combining subsystem 214 may also provide laseramplification of the sub-beams, preferably following the splitting ofthe output beam of seed laser 212 into sub-beams and prior to thecombining of the sub-beams to form output beam 222. Here, by way ofexample, splitting and combining subsystem 214 is shown to include aplurality of optical amplifiers 224 located along corresponding ones ofchannels 216 for amplifying each sub-beam. It is appreciated, however,that such amplification is optional and may be omitted, depending on thepower output requirements of OPA laser 200.

The phase of output beam 222, and hence the position and shape of thefar-field intensity pattern thereof, is controlled, at least in part, bythe relative phases of the constituent sub-beams combined to form outputbeam 222. In many applications, such as laser additive manufacturing asillustrated in FIG. 2A, it is desirable to dynamically move and shapethe far-field intensity pattern of the output beam. This may be achievedin laser system 200 by laser splitting and combining subsystem 214dynamically varying the relative phases of the individual sub-beams andthereby varying the phase of the combined laser output 222 so asdynamically to control the position and shape of the far-field intensitypattern thereof.

The relative phases of the sub-beams are preferably predetermined inaccordance with the desired laser output pattern for the 3D printing ofitem 206. Particularly preferably, the varying relative phases areapplied by a phase control subsystem 230. Phase control subsystem 230preferably forms a part of a control electronics module 232 in OPA laser200 and preferably controls each phase modulator 218 so as todynamically modulate the relative phases of the sub-beams along channels216.

Due to noise inherent in OPA system 200, output beam 222 has noise.Noise in output beam 222 is typically phase noise created by thermal ormechanical effects and/or by the amplification process in the case thatoptical amplifiers 224 are present in OPA system 200. It is a particularfeature of a preferred embodiment of the present invention that lasersystem 200 includes a noise cancellation subsystem 240 operative toprovide a noise cancellation phase correction output in order to cancelout the noise in output beam 222 in a manner detailed henceforth.

Particularly preferably, noise cancellation subsystem 240 employs analgorithm to sense and correct phase noise in the combined laser output.The noise cancellation phase correction output is preferably provided bynoise cancellation subsystem 240 to phase modulator 218 so as to correctphase noise in output beam 222 and thus avoid distortion of the shapeand position of the far field intensity pattern of output beam 222 thatwould otherwise be caused by the noise. Noise cancellation subsystem 240may be included in control electronics module 232.

It is understood that output beam 222 may be additionally oralternatively affected by types of noise other than phase noise,including intensity noise. In the case of output beam 222 havingintensity noise, noise cancellation subsystem 240 may be operative toprovide a noise cancellation phase correction output in order to cancelout the intensity noise in output beam 222. In such a case, OPA lasersystem 200 may optionally additionally include intensity modulators 242along channels 216 for modulating the intensity of each of the sub-beamsalong channels 216.

It is understood that output beam 222 may be additionally oralternatively affected by mechanical noise which may affect the relativeposition of the sub-beams. In the case of output beam 222 havingposition noise, noise cancellation subsystem 240 may be operative toprovide a noise cancellation phase correction output in order to cancelout the position noise in output beam 222. In such a case, OPA lasersystem 200 may optionally additionally include position modulators 244along channels 216 for modulating the position of each of the sub-beamsalong channels 216.

In order to facilitate application of phase variation and noisecorrection to output beam 222, a portion of the output of OPA laser 200is preferably extracted and directed towards at least one detector, hereillustrated as a single detector 250. Detector 250 may alternatively beembodied as multiple detectors, as detailed henceforth with reference toFIGS. 6-8 and 15-21 . The extracted portion of the output beampreferably functions as a reference beam, based on characteristics ofwhich the required noise correction and/or phase variation may becalculated. In the embodiment shown in FIG. 2A, plurality of sub-beamsalong channels 216 are directed towards a beam splitter 260. Beamsplitter 260 preferably splits each sub-beam into a transmitted portion262 and a reflected portion 264 in accordance with a predeterminedratio. For example, beam splitter 260 may split each sub-beam with a99.9% transmitted: 0.01% reflected ratio.

The transmitted portion 262 of the sub-beams preferably propagatestowards focal lens 220, at which focal lens 220 the sub-beams arecombined to form output beam 222 having a far-field intensity pattern266 incident on scanning mirror 203. The reflected portion 264 of thesub-beams is preferably reflected towards an additional focal lens 268,at which additional focal lens 268 the sub-beams are combined to form anoutput reference beam 270 having a far-field intensity pattern 272incident on a surface of detector 250.

It is understood that the particular structure and configuration of beamsplitting and recombining elements shown herein, including beam splitter260 and focal lenses 220 and 268, is exemplary only and depicted in ahighly simplified form. It is appreciated that OPA laser system 200 mayinclude a variety of such elements, as well as additional opticalelements, including, by way of example only, additional or alternativelenses, optical fibers and coherent free-space far-field combiners.

As described hereinabove, the shape and position of far-field intensitypattern 266 of the output beam 222 and correspondingly of far-fieldintensity pattern 272 of the reference beam 270 are constantly changing,due to the ongoing variation of the relative phases of the sub-beams. Asa result, far-field intensity pattern 272 is not fixed upon detector 250but rather is constantly being moved around with respect to detector 250depending on the combined relative phases of the constituent sub-beams.However, in order for detector 250 to provide the required noisecancellation phase correction output, far-field intensity pattern 272must be incident upon detector 250 in order for detector to measure theintensity of far-field intensity pattern 272 and hence apply a noisecorrection accordingly, resulting in a fixed output beam.

The conflict between the dynamic nature of far-field intensity pattern272 due to the phase-variation thereof and the fixed nature required offar-field intensity pattern 272 in order to derive and apply noisecorrection thereto, is advantageously resolved in the present inventionby providing the noise cancellation and phase variation at mutuallydifferent times and rates.

The noise cancellation phase correction output is provided based ontaking into consideration noise measured at detector 250 at a noisesampling rate. The output beam 222 is controlled in such a way that thefar-field intensity pattern 272 is incident upon detector 250 during thecourse of the dynamic changes to the shape and position of output andreference far-field intensity patterns 266 and 272 at a rate that isequal to or higher than the required noise sampling rate. The noise inreference beam 270 is taken into consideration during those intermittenttimes at which the far-field intensity pattern 272 is returned todetector 250.

At time interstices between the intermittent times at which far-fieldintensity pattern 272 is incident upon detector 250, the phase of thecombined output beams 222, 270 is varied in order to dynamically changethe shape and position of the far-field intensity pattern thereof asrequired to perform additive manufacturing of item 206. The combinedlaser output is varied at a phase varying rate which exceeds the noisesampling rate, in order to rapidly change the phase and hence shape andposition of the far-field intensity pattern. By way of example, thenoise sampling rate may be of the order of 10-1000 Hz whereas the phasevarying rate may be greater than 10,000 Hz.

The different rates and time scales over which the noise cancellationand phase variation are preferably performed in embodiments of thepresent invention may be best understood with reference to a graph 280seen in FIG. 2A and an enlarged version thereof shown in FIG. 2B.

As seen most clearly in FIG. 2B, graph 280 includes an upper portion 282displaying variation in intensity over time of far-field intensitypattern 272 as measured at detector 250 and a lower portion 284,displaying variation over the same time period of the relative phases ofa number of sub-beams contributing to output beam 222 and reference beam270. For the sake of simplicity, the relative phases of ten sub-beamsare displayed in graph 280, although it is appreciated that OPA system200 and hence the explanation provided herein is applicable to a feweror, more typically, a far greater number of sub-beams.

As seen in upper portion 282, intensity peaks 286 represent measuredintensity of the reference beam 270 when the far field intensity pattern272 passes over detector 250. As seen in lower portion 284, intensitypeaks 286 occur at intermittent times T_(i) at which the relative phaseof each sub-beam is zero, meaning that there is no shift in phasebetween the sub-beams, the position of the combined output beam istherefore not being changed and the far field intensity pattern 272 ishence directly incident on the detector 250. It is understood thatdetector 250 may alternatively be positioned such that the relativephase of the sub-beams thereat is non-zero. Furthermore, more than asingle detector may be employed so as to allow measurement of the farfield intensity pattern 272 at more than one location therealong, asdetailed henceforth with reference to FIGS. 6-8 and 15-21 .

Between intensity peaks 286 the measured intensity is close to zero, asthe far-field intensity pattern 272 is moved to the either side ofdetector 250 and thus is not directly incident on the detector 250. Asappreciated from consideration of upper portion 282, the magnitude ofintensity peaks 286 is not constant due to the presence of noise in thelaser output beam, which noise degrades the far field intensity pattern272.

As seen in lower portion 284, the relative phases of the sub-beams arevaried at time interstices T_(between) between intermittent times T_(i).In the phase variation function illustrated herein, the relative phasesof the sub-beams are shown to be varied in a periodic, regularlyrepeating pattern, with equal phase shifts being applied in the positiveand negative directions. It is appreciated that such a simplisticpattern is illustrative only and that the phase variation is notnecessarily regularly repeating, nor necessarily symmetrical in positiveand negative directions. Furthermore, it is understood that timeinterstices T_(between) preferably but not necessarily do not overlapwith intermittent times T_(i). Additionally, it is appreciated that atleast one of the phase varying rate and the noise sampling rate may beconstant or may change over time.

Noise cancellation subsystem 240 preferably operates by taking intoconsideration the noise at intermittent times T_(i) and providing anoise cancellation phase correction output based on the noise sensed atintermittent times T_(i). Noise cancellation subsystem 240 preferablyemploys an algorithm in order to sense noise and correct for the sensednoise accordingly.

According to one exemplary embodiment of the present invention, noisecancellation subsystem 240 employs an algorithm in which the relativephase of one channel is changed in such a way that the relative phase ismodified by a given phase change Δφ during each cycle of travel of thefar-field intensity pattern 272 with respect to detector 250. Followinga number of such cycles, in which a different phase change Δφ is appliedto the selected sub-beam over each cycle, the algorithm ascertains themaximum output intensity over all of the cycles and finds the optimumphase change Δφ that produced this maximum intensity. The phase changeof the selected sub-beam is then fixed at the optimum phase change Δφfor subsequent cycles and the algorithm proceeds to optimize anothersub-beam.

Graph 280 illustrates noise cancellation according to this exemplaryalgorithm in three sub-beams or channels A, B and C of the total of 10sub-beams. Sub-beams A, B and C are displayed alone in FIG. 2C for thesake of clarity. It is appreciated that the line style of the tracesrepresenting phase variation and noise correction of sub-beams A, B andC respectively is modified in FIG. 2C in comparison to FIGS. 2A and 2B,in order to aid differentiation between the various sub-beams for thepurposes of the explanation hereinbelow.

As seen initially in the case of channel A, and appreciated most clearlyfrom consideration of an enlargement 290, the dashed trace representsthe pattern of variation in relative phase of sub-beam A, as would beapplied by phase control sub-system 230 in the absence of any noisecorrection. This trace may be termed A_(uncorrected). The dotted- anddashed trace represents the actual relative phase of sub-beam A asmodified by the noise correction algorithm in order to find the optimumphase noise correction. This trace may be termed A_(corrected). Themodified relative phase of A_(corrected) is shifted with respect to thenon-modified relative phase of A_(uncorrected) by a different Δφ_(A)over the first five cycles of sub-beam A. The intensity 286 measured atdetector 250 varies over the first five cycles of optimization ofsub-beam A due to the deliberate change in relative phase shift.

Following the first five cycles of sub-beam A, the algorithm ascertainsthe maximum intensity and finds the phase change Δφ_(A) that producesthe maximum intensity. In this case, the maximum intensity is seen to beIA_(max) produced by the second phase shift Δφ_(A). The phase changeapplied to relative phase variation of sub-beam A is thus fixed at thesecond phase shift Δφ_(A) for subsequent cycles and the algorithmproceeds to optimize sub-beam B.

It is appreciated that during the sequential cycles of optimization ofsub-beam A, the relative phases of the remainder of the sub-beams arevaried as usual, each at a phase varying rate that far exceeds the noisesampling rate at which the noise in sub-beam A is taken intoconsideration.

As seen further in the case of sub-beam B, and appreciated most clearlyfrom consideration of an enlargement 292, the thicker trace duringoptimization of channel B represents the pattern of variation inrelative phase of sub-beam B, as would be applied by phase controlsub-system 230 in the absence of any noise correction. This trace may betermed B_(uncorrected). The thinner trace during optimization of channelB represents the actual relative phase of sub-beam B as modified by thenoise correction algorithm in order to find the optimum phase noisecorrection. This trace may be termed B_(corrected). The modifiedrelative phase of B_(corrected) is shifted with respect to thenon-modified relative phase of B_(uncorrected) by a different Δφ_(B)over five cycles of optimization sub-beam B. The intensity 286 measuredat detector 250 varies over these five cycles of optimization sub-beam Bdue to the deliberate change in relative phase shift.

Following these five cycles of sub-beam B, the algorithm ascertains themaximum intensity and finds the phase change Δφ_(B) that produces themaximum intensity. In this case, the maximum intensity is seen to beIAB_(max) produced by the fourth phase shift Δφ_(B). The phase changeapplied to relative phase variation of sub-beam B is then fixed at thefourth phase shift Δφ_(B) for subsequent cycles and the algorithmproceeds to optimize sub-beam C.

It is appreciated that during the five cycles of optimization ofsub-beam B, the relative phases of the remainder of the sub-beams arevaried as usual, each at a phase varying rate that far exceeds the noisesampling rate at which the noise in sub-beam B is taken intoconsideration.

A similar optimization process is preferably implemented for sub-beam C,in which a phase change Δφ_(C) is applied over several cycles in orderto optimize the output beam intensity and correct for intensitydegradation thereof due to phase noise in sub-beam C.

Detector 250 may operate continuously in order to continuously optimizethe relative phases of the sub-beams and correct for phase noisetherein. However, due to a finite response time of detector 250,detector 250 only takes into consideration the noise in reference beam270 at intermittent times, at a relatively slow noise sampling rate. Thenoise sampling rate is preferably but not necessarily predetermined. Thenoise sampling rate may alternatively be random.

It is appreciated that the particular parameters of the noise correctionalgorithm depicted in graph 280 are exemplary only and may be readilymodified, as will be understood by one skilled in the art. For example,the phase shift Δφ may be optimized over a greater or fewer number ofcycles than illustrated herein, each sub-beam may be fully optimizedeach time the sub-beam passes over detector 250 or several sub-beams orall of the sub-beams may be optimized during each cycle in which thefar-field intensity pattern passes over detector 250. Furthermore,non-sequential noise correction optimization algorithms mayalternatively be implemented, including, but not limited to, Stochasticparallel gradient descent optimization algorithms.

The use of dynamically shaped, noise corrected optical phased arrayoutput beams for laser additive manufacturing is highly advantageous andenables rapid beam steering, fast power modulation, fast beam focusingand beam shape tailoring. Both the speed and quality with which an itemmay be manufactured are improved using dynamically shaped, noisecorrected optical phase array output in comparison to conventional laser3D printing methods. It is appreciated that but for the provision ofnoise correction, in accordance with preferred embodiments of thepresent invention, the shape and position of the optical phased arrayoutput beam would be degraded, thereby degrading the quality, speed andprecision of the laser additive manufacturing process.

In order to maintain output beam intensity as the far-field intensitypattern of the beam moves, as is advantageous in certain additivemanufacturing applications, movement of the output beam may becontrolled such that the beam spends more time at lower-intensitypositions so as to compensate for reduced power delivery thereat.Additionally or alternatively, an intensity profile mask such as an NDfilter may be applied to the output beam in order to modify theintensity thereof.

Reference is now made to FIG. 3A, which is a simplified schematicillustration of an optical phased array laser system for noise correcteddynamic beam shaping, constructed and operative in accordance with afurther preferred embodiment of the present invention; and to FIGS. 3Band 3C, which are simplified graphical representations of phasevariation and noise correction in a system of the type illustrated inFIG. 3A.

As seen in FIG. 3A, there is provided an optical phased array (OPA)laser system 300, here shown to be employed, by way of example, within afree space optical communication system 302. Free space opticalcommunication system 302 may include OPA laser system 300 mounted at anoutdoor location, such as on a building, in spaced relation to areceiver 303 for receiving optical signals emanating from OPA laser 300.It is understood that although free space optical communication system302 is illustrated herein in the context of communication between twofixed points, free-space optical communication system 302 may be adaptedfor use in communications between two locations that are moving relativeto one another, as will be appreciated by one skilled in the art. It isfurther understood that although free space optical communication system302 is illustrated herein in the context of terrestrial communications,free-space optical communication system 302 may be adapted for use inextraterrestrial communications, as will be appreciated by one skilledin the art.

It is appreciated that free space optical communication system 302 isillustrated in FIG. 3A as including only a single OPA laser 300 andreceiver 303 for the sake of simplicity only, and may include a greaternumber of each, depending on the communication requirements of system302. It is further appreciated that receiver 303 may also be an OPAlaser of a type resembling OPA laser 300 and having receivingfunctionality. Furthermore, OPA laser 300 may include receivingfunctionality so as to allow duplex operation of OPA lasers 300 and 303,for transmission and reception of optical signals therebetween.

As best seen at an enlargement 310, OPA laser 300 preferably comprises aseed laser 312 and a laser beam splitting and combining subsystem 314.Splitting and combining subsystem 314 preferably receives an outputlaser beam from seed laser 312 and splits the output laser beam into aplurality of sub-beams along a corresponding plurality of channels 316.Here, by way of example only, an output from seed laser 312 is shown tobe split into ten sub-beams along ten channels 316 although it isappreciated that splitting and combining subsystem 314 may include afewer or greater number of channels along which the output of seed laser312 is split, and typically may include a far greater number of channelssuch as 32 or more channels.

The relative phase of each sub-beam may be individually modulated by aphase modulator 318, preferably located along each of channels 316. Eachphase modulated sub-beam produced by the splitting and subsequent phasemodulation of the output of seed laser 312 preferably propagates towardsa collimating lens 319. The individually collimated, phase modulatedsub-beams are subsequently combined, for example at a focal lens 320, toform an output beam 322.

Splitting and combining subsystem 314 may also provide laseramplification of the sub-beams, preferably following the splitting ofthe output beam of seed laser 312 into sub-beams and prior to thecombining of the sub-beams to form output beam 322. Here, by way ofexample, splitting and combining subsystem 314 is shown to include aplurality of optical amplifiers 324 located along corresponding ones ofchannels 316 for amplifying each sub-beam. It is appreciated, however,that such amplification is optional and may be omitted, depending on thepower output requirements of OPA laser 300.

The phase of output beam 322, and hence the position and shape of thefar-field intensity pattern thereof, is controlled, at least in part, bythe relative phases of the constituent sub-beams combined to form outputbeam 322. In many applications, such as free space opticalcommunications as illustrated in FIG. 3A, it is desirable to dynamicallymove and shape the far-field intensity pattern of the output beam. Thismay be achieved in laser system 300 by laser splitting and combiningsubsystem 314 dynamically varying the relative phases of the individualsub-beams and thereby varying the phase of the combined laser output 322so as dynamically to control the position and shape of the far-fieldintensity pattern thereof.

The relative phases of the sub-beams are preferably predetermined inaccordance with a desired laser output pattern for transmission toreceiver 303. Particularly preferably, the varying relative phases areapplied by a phase control subsystem 330. Phase control subsystem 330preferably forms a part of a control electronics module 332 in OPA laser300 and preferably controls each phase modulator 318 so as todynamically modulate the relative phases of the sub-beams along channels316.

Due to noise inherent in OPA system 300, output beam 322 has noise.Noise in output beam 322 is typically phase noise created by thermal ormechanical effects and/or by the amplification process in the case thatoptical amplifiers 324 are present in OPA system 300. It is a particularfeature of a preferred embodiment of the present invention that lasersystem 300 includes a noise cancellation subsystem 340 operative toprovide a noise cancellation phase correction output in order to cancelout the noise in output beam 322 in a manner detailed henceforth.

Particularly preferably, noise cancellation subsystem 340 employs analgorithm to sense and correct phase noise in the combined laser output.The noise cancellation phase correction output is preferably provided bynoise cancellation subsystem 340 to phase modulator 318 so as to correctphase noise in output beam 322 and thus avoid distortion of the shapeand position of the far field intensity pattern of output beam 322 thatwould otherwise be caused by the noise. Noise cancellation subsystem 340may be included in control electronics module 332.

It is understood that output beam 322 may be additionally oralternatively affected by types of noise other than phase noise,including intensity noise. In the case of output beam 322 havingintensity noise, noise cancellation subsystem 340 may be operative toprovide a noise cancellation phase correction output in order to cancelout the intensity noise in output beam 322. In such a case, OPA lasersystem 300 may optionally additionally include intensity modulators 342along channels 316 for modulating the intensity of each of the sub-beamsalong channels 316.

It is understood that output beam 322 may be additionally oralternatively affected by mechanical noise which may affect the relativeposition of the sub-beams. In the case of output beam 322 havingposition noise, noise cancellation subsystem 340 may be operative toprovide a noise cancellation phase correction output in order to cancelout the position noise in output beam 322. In such a case, OPA lasersystem 300 may optionally additionally include position modulators 344along channels 316 for modulating the position of each of the sub-beamsalong channels 316.

In order to facilitate application of phase variation and noisecorrection to output beam 322, a portion of the output of OPA laser 300is preferably extracted and directed towards at least one detector, hereillustrated as a single detector 350. Detector 350 may alternatively beembodied as multiple detectors, as detailed henceforth with reference toFIGS. 6-8 and 15-21 . The extracted portion of the output beampreferably functions as a reference beam, based on characteristics ofwhich the required noise correction and/or phase variation may becalculated. In the embodiment shown in FIG. 3A, plurality of sub-beamsalong channels 316 are directed towards a beam splitter 360. Beamsplitter 360 preferably splits each sub-beam into a transmitted portion362 and a reflected portion 364 in accordance with a predeterminedratio. For example, beam splitter 360 may split each sub-beam with a99.9% transmitted: 0.01% reflected ratio.

The transmitted portion 362 of the sub-beams preferably propagatestowards focal lens 320, at which focal lens 320 the sub-beams arecombined to form output beam 322 having a far-field intensity pattern366. The reflected portion 364 of the sub-beams is preferably reflectedtowards an additional focal lens 368, at which additional focal lens 368the sub-beams are combined to form an output reference beam 370 having afar-field intensity pattern 372 incident on a surface of detector 350.

It is understood that the particular structure and configuration of beamsplitting and recombining elements shown herein, including beam splitter360 and focal lenses 320 and 368, is exemplary only and depicted in ahighly simplified form. It is appreciated that OPA laser system 300 mayinclude a variety of such elements, as well as additional opticalelements, including, by way of example only, additional or alternativelenses, optical fibers and coherent free-space far-field combiners.

As described hereinabove, the shape and position of far-field intensitypattern 366 of the output beam 322 and correspondingly of far-fieldintensity pattern 372 of the reference beam 370 are constantly changing,due to the ongoing variation of the relative phases of the sub-beams. Asa result, far-field intensity pattern 372 is not fixed upon detector 350but rather is constantly being moved around with respect to detector 350depending on the combined relative phases of the constituent sub-beams.However, in order for detector 350 to provide the required noisecancellation phase correction output, far-field intensity pattern 372must be incident upon detector 350 in order for detector to measure theintensity of far-field intensity pattern 372 and hence apply a noisecorrection accordingly, resulting in a fixed output beam.

The conflict between the dynamic nature of far-field intensity pattern372 due to the phase-variation thereof and the fixed nature required offar-field intensity pattern 372 in order to derive and apply noisecorrection thereto, is advantageously resolved in the present inventionby providing the noise cancellation and phase variation at mutuallydifferent times and rates.

The noise cancellation phase correction output is provided based ontaking into consideration noise measured at detector 350 at a noisesampling rate. The output beam 322 is controlled in such a way that thefar-field intensity pattern 372 is incident upon detector 350 during thecourse of the dynamic changes to the shape and position of output andreference far-field intensity patterns 366 and 372 at a rate that isequal to or higher than the required noise sampling rate. The noise inreference beam 370 is taken into consideration during those intermittenttimes at which the far-field intensity pattern 372 is returned todetector 350.

At time interstices between the intermittent times at which far-fieldintensity pattern 372 is incident upon detector 350, the phase of thecombined output beams 322, 370 is varied in order to dynamically changethe shape and position of the far-field intensity pattern thereof asrequired to perform additive manufacturing of item 206. The combinedlaser output is varied at a phase varying rate which exceeds the noisesampling rate, in order to rapidly change the phase and hence shape andposition of the far-field intensity pattern. By way of example, thenoise sampling rate may be of the order of 10-1000 Hz whereas the phasevarying rate may be greater than 10,000 Hz.

The different rates and time scales over which the noise cancellationand phase variation are preferably performed in embodiments of thepresent invention may be best understood with reference to a graph 380seen in FIG. 3A and an enlarged version thereof shown in FIG. 3B.

As seen most clearly in FIG. 3B, graph 380 includes an upper portion 382displaying variation in intensity over time of far-field intensitypattern 372 as measured at detector 350 and a lower portion 384,displaying variation over the same time period of the relative phases ofa number of sub-beams contributing to output beam 322 and reference beam370. For the sake of simplicity, the relative phases of ten sub-beamsare displayed in graph 380, although it is appreciated that OPA system300 and hence the explanation provided herein is applicable to a feweror, more typically, a far greater number of sub-beams.

As seen in upper portion 382, intensity peaks 386 represent measuredintensity of the reference beam 370 when the far field intensity pattern372 passes over detector 350. As seen in lower portion 384, intensitypeaks 386 occur at intermittent times T_(i) at which the relative phaseof each sub-beam is zero, meaning that there is no shift in phasebetween the sub-beams, the position of the combined output beam istherefore not being changed and the far field intensity pattern 372 ishence directly incident on the detector 350. It is understood thatdetector 350 may alternatively be positioned such that the relativephase of the sub-beams thereat is non-zero. Furthermore, more than asingle detector may be employed so as to allow measurement of the farfield intensity pattern 372 at more than one location therealong, asdetailed henceforth with reference to FIGS. 6-8 and 15-21 .

Between intensity peaks 386 the measured intensity is close to zero, asthe far-field intensity pattern 372 is moved to the either side ofdetector 350 and thus is not directly incident on the detector 350. Asappreciated from consideration of upper portion 382, the magnitude ofintensity peaks 386 is not constant due to the presence of noise in thelaser output beam, which noise degrades the far field intensity pattern372.

As seen in lower portion 384, the relative phases of the sub-beams arevaried at time interstices T_(between) between intermittent times T_(i).In the phase variation function illustrated herein, the relative phasesof the sub-beams are shown to be varied in a periodic, regularlyrepeating pattern, with equal phase shifts being applied in the positiveand negative directions. It is appreciated that such a simplisticpattern is illustrative only and that the phase variation is notnecessarily regularly repeating, nor necessarily symmetrical in positiveand negative directions. Furthermore, it is understood that timeinterstices T_(between) preferably but not necessarily do not overlapwith intermittent times T_(i). Additionally, it is appreciated that atleast one of the phase varying rate and the noise sampling rate may beconstant or may change over time.

Noise cancellation subsystem 340 preferably operates by taking intoconsideration the noise at intermittent times T_(i) and providing anoise cancellation phase correction output based on the noise sensed atintermittent times Noise cancellation subsystem 340 preferably employsan algorithm in order to sense noise and correct for the sensed noiseaccordingly.

According to one exemplary embodiment of the present invention, noisecancellation subsystem 340 employs an algorithm in which the relativephase of one channel is changed in such a way that the relative phase ismodified by a given phase change Δφ during each cycle of travel of thefar-field intensity pattern 372 with respect to detector 350. Followinga number of such cycles, in which a different phase change Δφ is appliedto the selected sub-beam over each cycle, the algorithm ascertains themaximum output intensity over all of the cycles and finds the optimumphase change Δ_(T) that produced this maximum intensity. The phasechange of the selected sub-beam is then fixed at the optimum phasechange Δφ for subsequent cycles and the algorithm proceeds to optimizeanother sub-beam.

Graph 380 illustrates noise cancellation according to this exemplaryalgorithm in three sub-beams or channels A, B and C of the total of 10sub-beams. Sub-beams A, B and C are displayed alone in FIG. 3C for thesake of clarity. It is appreciated that the line style of the tracesrepresenting phase variation and noise correction of sub-beams A, B andC respectively is modified in FIG. 3C in comparison to FIGS. 3A and 3B,in order to aid differentiation between the various sub-beams for thepurposes of the explanation hereinbelow.

As seen initially in the case of channel A, and appreciated most clearlyfrom consideration of an enlargement 390, the dashed trace representsthe pattern of variation in relative phase of sub-beam A, as would beapplied by phase control sub-system 330 in the absence of any noisecorrection. This trace may be termed A_(uncorrected). The dotted- anddashed trace represents the actual relative phase of sub-beam A asmodified by the noise correction algorithm in order to find the optimumphase noise correction. This trace may be termed A_(corrected). Themodified relative phase of A_(corrected) is shifted with respect to thenon-modified relative phase of A_(uncorrected) by a different Δφ_(A)over the first five cycles of sub-beam A. The intensity 386 measured atdetector 350 varies over the first five cycles of optimization ofsub-beam A due to the deliberate change in relative phase shift.

Following the first five cycles of sub-beam A, the algorithm ascertainsthe maximum intensity and finds the phase change Δφ_(A) that producesthe maximum intensity. In this case, the maximum intensity is seen to beIA_(max) produced by the second phase shift Δφ_(A). The phase changeapplied to relative phase variation of sub-beam A is thus fixed at thesecond phase shift Δφ_(A) for subsequent cycles and the algorithmproceeds to optimize sub-beam B.

It is appreciated that during the sequential cycles of optimization ofsub-beam A, the relative phases of the remainder of the sub-beams arevaried as usual, each at a phase varying rate that far exceeds the noisesampling rate at which the noise in sub-beam A is taken intoconsideration.

As seen further in the case of sub-beam B, and appreciated most clearlyfrom consideration of an enlargement 392, the thicker trace duringoptimization of channel B represents the pattern of variation inrelative phase of sub-beam B, as would be applied by phase controlsub-system 330 in the absence of any noise correction. This trace may betermed B_(uncorrected). The thinner trace during optimization of channelB represents the actual relative phase of sub-beam B as modified by thenoise correction algorithm in order to find the optimum phase noisecorrection. This trace may be termed B_(corrected). The modifiedrelative phase of B_(corrected) is shifted with respect to thenon-modified relative phase of B_(uncorrected) by a different Δφ_(B)over five cycles of optimization sub-beam B. The intensity 386 measuredat detector 350 varies over these five cycles of optimization sub-beam Bdue to the deliberate change in relative phase shift.

Following these five cycles of sub-beam B, the algorithm ascertains themaximum intensity and finds the phase change Δφ_(B) that produces themaximum intensity. In this case, the maximum intensity is seen to beIAB_(max) produced by the fourth phase shift Δφ_(B). The phase changeapplied to relative phase variation of sub-beam B is then fixed at thefourth phase shift Δφ_(B) for subsequent cycles and the algorithmproceeds to optimize sub-beam C.

It is appreciated that during the five cycles of optimization ofsub-beam B, the relative phases of the remainder of the sub-beams arevaried as usual, each at a phase varying rate that far exceeds the noisesampling rate at which the noise in sub-beam B is taken intoconsideration.

A similar optimization process is preferably implemented for sub-beam C,in which a phase change Δφ_(C) is applied over several cycles in orderto optimize the output beam intensity and correct for intensitydegradation thereof due to phase noise in sub-beam C.

Detector 350 may operate continuously in order to continuously optimizethe relative phases of the sub-beams and correct for phase noisetherein. However, due to a finite response time of detector 350,detector 350 only takes into consideration the noise in reference beam370 at intermittent times, at a relatively slow noise sampling rate. Thenoise sampling rate is preferably but not necessarily predetermined. Thenoise sampling rate may alternatively be random.

It is appreciated that the particular parameters of the noise correctionalgorithm depicted in graph 380 are exemplary only and may be readilymodified, as will be understood by one skilled in the art. For example,the phase shift Δφ may be optimized over a greater or fewer number ofcycles than illustrated herein, each sub-beam may be fully optimizedeach time the sub-beam passes over detector 350 or several sub-beams orall of the sub-beams may be optimized during each cycle in which thefar-field intensity pattern passes over detector 350. Furthermore,non-sequential noise correction optimization algorithms mayalternatively be implemented, including, but not limited to, Stochasticparallel gradient descent optimization algorithms.

The use of dynamically shaped, noise corrected optical phased arrayoutput beams for free-space optical communication is highly advantageousand enables rapid beam steering, fast power modulation, fast beamfocusing and beam shape tailoring. Both the speed and quality ofcommunication are improved using dynamically shaped, noise correctedoptical phase array output in comparison to conventional free spaceoptical communication methods. It is appreciated that but for theprovision of noise correction, in accordance with preferred embodimentsof the present invention, the shape and position of the optical phasedarray output beam would be degraded, thereby degrading the quality,speed and precision of the transmitted laser output.

In order to maintain output beam intensity as the far-field intensitypattern of the beam moves, as is advantageous in certain opticalcommunication applications, movement of the output beam may becontrolled such that the beam spends more time at lower-intensitypositions so as to compensate for reduced power delivery thereat.Additionally or alternatively, an intensity profile mask such as an NDfilter may be applied to the output beam in order to modify theintensity thereof.

Reference is now made to FIG. 4A, which is a simplified schematicillustration of an optical phased array laser system for noise correcteddynamic beam shaping, constructed and operative in accordance with yetanother preferred embodiment of the present invention; and to FIGS. 4Band 4C, which are simplified graphical representations of phasevariation and noise correction in a system of the type illustrated inFIG. 4A.

As seen in FIG. 4A, there is provided an optical phased array (OPA)laser system 400, here shown to be employed, by way of example, within alaser welding system 402. Laser welding system 402 may include OPA lasersystem 400 mounted on or within a portion of a laser welding robot 404.An item, such as an item 406, may be welded by laser welding robot 404,as is detailed henceforth. It is understood that although laser weldingsystem 402 is illustrated herein in the context of welding robot 404,system 402 may be adapted for use in any welding setup, as will beappreciated by one skilled in the art.

As best seen at an enlargement 410, OPA laser 400 preferably comprises aseed laser 412 and a laser beam splitting and combining subsystem 414.Splitting and combining subsystem 414 preferably receives an outputlaser beam from seed laser 412 and splits the output laser beam into aplurality of sub-beams along a corresponding plurality of channels 416.Here, by way of example only, an output from seed laser 412 is shown tobe split into ten sub-beams along ten channels 416 although it isappreciated that splitting and combining subsystem 414 may include afewer or greater number of channels along which the output of seed laser412 is split, and typically may include a far greater number of channelssuch as 32 or more channels.

The relative phase of each sub-beam may be individually modulated by aphase modulator 418, preferably located along each of channels 416. Eachphase modulated sub-beam produced by the splitting and subsequent phasemodulation of the output of seed laser 412 preferably propagates towardsa collimating lens 419. The individually collimated, phase modulatedsub-beams are subsequently combined, for example at a focal lens 420, toform an output beam 422.

Splitting and combining subsystem 414 may also provide laseramplification of the sub-beams, preferably following the splitting ofthe output beam of seed laser 412 into sub-beams and prior to thecombining of the sub-beams to form output beam 422. Here, by way ofexample, splitting and combining subsystem 414 is shown to include aplurality of optical amplifiers 424 located along corresponding ones ofchannels 416 for amplifying each sub-beam. It is appreciated, however,that such amplification is optional and may be omitted, depending on thepower output requirements of OPA laser 400.

The phase of output beam 422, and hence the position and shape of thefar-field intensity pattern thereof, is controlled, at least in part, bythe relative phases of the constituent sub-beams combined to form outputbeam 422. In many applications, such as laser welding as illustrated inFIG. 4A, it is desirable to dynamically move and shape the far-fieldintensity pattern of the output beam. This may be achieved in lasersystem 400 by laser splitting and combining subsystem 414 dynamicallyvarying the relative phases of the individual sub-beams and therebyvarying the phase of the combined laser output 422 so as dynamically tocontrol the position and shape of the far-field intensity patternthereof.

The relative phases of the sub-beams are preferably predetermined inaccordance with the desired laser output pattern for the welding of item406. Particularly preferably, the varying relative phases are applied bya phase control subsystem 430. Phase control subsystem 430 preferablyforms a part of a control electronics module 432 in OPA laser 400 andpreferably controls each phase modulator 418 so as to dynamicallymodulate the relative phases of the sub-beams along channels 416.

Due to noise inherent in OPA system 400, output beam 422 has noise.Noise in output beam 422 is typically phase noise created by thermal ormechanical effects and/or by the amplification process in the case thatoptical amplifiers 424 are present in OPA system 400. It is a particularfeature of a preferred embodiment of the present invention that lasersystem 400 includes a noise cancellation subsystem 440 operative toprovide a noise cancellation phase correction output in order to cancelout the noise in output beam 422 in a manner detailed henceforth.

Particularly preferably, noise cancellation subsystem 440 employs analgorithm to sense and correct phase noise in the combined laser output.The noise cancellation phase correction output is preferably provided bynoise cancellation subsystem 440 to phase modulator 418 so as to correctphase noise in output beam 422 and thus avoid distortion of the shapeand position of the far field intensity pattern of output beam 422 thatwould otherwise be caused by the noise. Noise cancellation subsystem 440may be included in control electronics module 432.

It is understood that output beam 422 may be additionally oralternatively affected by types of noise other than phase noise,including intensity noise. In the case of output beam 422 havingintensity noise, noise cancellation subsystem 440 may be operative toprovide a noise cancellation phase correction output in order to cancelout the intensity noise in output beam 422. In such a case, OPA lasersystem 400 may optionally additionally include intensity modulators 442along channels 416 for modulating the intensity of each of the sub-beamsalong channels 416.

It is understood that output beam 422 may be additionally oralternatively affected by mechanical noise which may affect the relativeposition of the sub-beams. In the case of output beam 422 havingposition noise, noise cancellation subsystem 440 may be operative toprovide a noise cancellation phase correction output in order to cancelout the position noise in output beam 422. In such a case, OPA lasersystem 400 may optionally additionally include position modulators 444along channels 416 for modulating the position of each of the sub-beamsalong channels 416.

In order to facilitate application of phase variation and noisecorrection to output beam 422, a portion of the output of OPA laser 400is preferably extracted and directed towards at least one detector, hereillustrated as a single detector 450. Detector 450 may alternatively beembodied as multiple detectors, as detailed henceforth with reference toFIGS. 6-8 and 15-21 . The extracted portion of the output beampreferably functions as a reference beam, based on characteristics ofwhich the required noise correction and/or phase variation may becalculated. In the embodiment shown in FIG. 4A, plurality of sub-beamsalong channels 416 are directed towards a beam splitter 460. Beamsplitter 460 preferably splits each sub-beam into a transmitted portion462 and a reflected portion 464 in accordance with a predeterminedratio. For example, beam splitter 460 may split each sub-beam with a99.9% transmitted: 0.01% reflected ratio.

The transmitted portion 462 of the sub-beams preferably propagatestowards focal lens 420, at which focal lens 420 the sub-beams arecombined to form output beam 422 having a far-field intensity pattern466 incident on item 406. The reflected portion 464 of the sub-beams ispreferably reflected towards an additional focal lens 468, at whichadditional focal lens 468 the sub-beams are combined to form an outputreference beam 470 having a far-field intensity pattern 472 incident ona surface of detector 450.

It is understood that the particular structure and configuration of beamsplitting and recombining elements shown herein, including beam splitter460 and focal lenses 420 and 468, is exemplary only and depicted in ahighly simplified form. It is appreciated that OPA laser system 400 mayinclude a variety of such elements, as well as additional opticalelements, including, by way of example only, additional or alternativelenses, optical fibers and coherent free-space far-field combiners.

As described hereinabove, the shape and position of far-field intensitypattern 466 of the output beam 422 and correspondingly of far-fieldintensity pattern 472 of the reference beam 470 are constantly changing,due to the ongoing variation of the relative phases of the sub-beams. Asa result, far-field intensity pattern 472 is not fixed upon detector 450but rather is constantly being moved around with respect to detector 450depending on the combined relative phases of the constituent sub-beams.However, in order for detector 450 to provide the required noisecancellation phase correction output, far-field intensity pattern 472must be incident upon detector 450 in order for detector to measure theintensity of far-field intensity pattern 472 and hence apply a noisecorrection accordingly, resulting in a fixed output beam.

The conflict between the dynamic nature of far-field intensity pattern472 due to the phase-variation thereof and the fixed nature required offar-field intensity pattern 472 in order to derive and apply noisecorrection thereto, is advantageously resolved in the present inventionby providing the noise cancellation and phase variation at mutuallydifferent times and rates.

The noise cancellation phase correction output is provided based ontaking into consideration noise measured at detector 450 at a noisesampling rate. The output beam 422 is controlled in such a way that thefar-field intensity pattern 472 is incident upon detector 450 during thecourse of the dynamic changes to the shape and position of output andreference far-field intensity patterns 466 and 472 at a rate that isequal to or higher than the required noise sampling rate. The noise inreference beam 470 is taken into consideration during those intermittenttimes at which the far-field intensity pattern 472 is returned todetector 450.

At time interstices between the intermittent times at which far-fieldintensity pattern 472 is incident upon detector 450, the phase of thecombined output beams 422, 470 is varied in order to dynamically changethe shape and position of the far-field intensity pattern thereof asrequired to perform laser welding of item 406. The combined laser outputis varied at a phase varying rate which exceeds the noise sampling rate,in order to rapidly change the phase and hence shape and position of thefar-field intensity pattern. By way of example, the noise sampling ratemay be of the order of 10-1000 Hz whereas the phase varying rate may begreater than 10,000 Hz.

The different rates and time scales over which the noise cancellationand phase variation are preferably performed in embodiments of thepresent invention may be best understood with reference to a graph 480seen in FIG. 4A and an enlarged version thereof shown in FIG. 4B.

As seen most clearly in FIG. 4B, graph 480 includes an upper portion 482displaying variation in intensity over time of far-field intensitypattern 472 as measured at detector 450 and a lower portion 484,displaying variation over the same time period of the relative phases ofa number of sub-beams contributing to output beam 422 and reference beam470. For the sake of simplicity, the relative phases of ten sub-beamsare displayed in graph 480, although it is appreciated that OPA system400 and hence the explanation provided herein is applicable to a feweror, more typically, a far greater number of sub-beams.

As seen in upper portion 482, intensity peaks 486 represent measuredintensity of the reference beam 470 when the far field intensity pattern472 passes over detector 450. As seen in lower portion 484, intensitypeaks 486 occur at intermittent times T_(i) at which the relative phaseof each sub-beam is zero, meaning that there is no shift in phasebetween the sub-beams, the position of the combined output beam istherefore not being changed and the far field intensity pattern 472 ishence directly incident on the detector 450. It is understood thatdetector 450 may alternatively be positioned such that the relativephase of the sub-beams thereat is non-zero. Furthermore, more than asingle detector may be employed so as to allow measurement of the farfield intensity pattern 472 at more than one location therealong, asdetailed henceforth with reference to FIGS. 6-8 and 15-21 .

Between intensity peaks 486 the measured intensity is close to zero, asthe far-field intensity pattern 472 is moved to the either side ofdetector 450 and thus is not directly incident on the detector 450. Asappreciated from consideration of upper portion 482, the magnitude ofintensity peaks 486 is not constant due to the presence of noise in thelaser output beam, which noise degrades the far field intensity pattern472.

As seen in lower portion 484, the relative phases of the sub-beams arevaried at time interstices T_(between) between intermittent times T_(i).In the phase variation function illustrated herein, the relative phasesof the sub-beams are shown to be varied in a periodic, regularlyrepeating pattern, with equal phase shifts being applied in the positiveand negative directions. It is appreciated that such a simplisticpattern is illustrative only and that the phase variation is notnecessarily regularly repeating, nor necessarily symmetrical in positiveand negative directions. Furthermore, it is understood that timeinterstices T_(between) preferably but not necessarily do not overlapwith intermittent times T_(i). Additionally, it is appreciated that atleast one of the phase varying rate and the noise sampling rate may beconstant or may change over time.

Noise cancellation subsystem 440 preferably operates by taking intoconsideration the noise at intermittent times T_(i) and providing anoise cancellation phase correction output based on the noise sensed atintermittent times T_(i). Noise cancellation subsystem 440 preferablyemploys an algorithm in order to sense noise and correct for the sensednoise accordingly.

According to one exemplary embodiment of the present invention, noisecancellation subsystem 440 employs an algorithm in which the relativephase of one channel is changed in such a way that the relative phase ismodified by a given phase change Δφ during each cycle of travel of thefar-field intensity pattern 472 with respect to detector 150. Followinga number of such cycles, in which a different phase change Δφ is appliedto the selected sub-beam over each cycle, the algorithm ascertains themaximum output intensity over all of the cycles and finds the optimumphase change Δφ that produced this maximum intensity. The phase changeof the selected sub-beam is then fixed at the optimum phase change Δφfor subsequent cycles and the algorithm proceeds to optimize anothersub-beam.

Graph 480 illustrates noise cancellation according to this exemplaryalgorithm in three sub-beams or channels A, B and C of the total of 10sub-beams. Sub-beams A, B and C are displayed alone in FIG. 4C for thesake of clarity. It is appreciated that the line style of the tracesrepresenting phase variation and noise correction of sub-beams A, B andC respectively is modified in FIG. 4C in comparison to FIGS. 4A and 4B,in order to aid differentiation between the various sub-beams for thepurposes of the explanation hereinbelow.

As seen initially in the case of channel A, and appreciated most clearlyfrom consideration of an enlargement 490, the dashed trace representsthe pattern of variation in relative phase of sub-beam A, as would beapplied by phase control sub-system 430 in the absence of any noisecorrection. This trace may be termed A_(uncorrected). The dotted- anddashed trace represents the actual relative phase of sub-beam A asmodified by the noise correction algorithm in order to find the optimumphase noise correction. This trace may be termed A_(corrected) Themodified relative phase of A_(corrected) is shifted with respect to thenon-modified relative phase of A_(uncorrected) by a different Δφ_(A)over the first five cycles of sub-beam A. The intensity 486 measured atdetector 450 varies over the first five cycles of optimization ofsub-beam A due to the deliberate change in relative phase shift.

Following the first five cycles of sub-beam A, the algorithm ascertainsthe maximum intensity and finds the phase change Δφ_(A) that producesthe maximum intensity. In this case, the maximum intensity is seen to beIA_(max) produced by the second phase shift Δφ_(A). The phase changeapplied to relative phase variation of sub-beam A is thus fixed at thesecond phase shift Δφ_(A) for subsequent cycles and the algorithmproceeds to optimize sub-beam B.

It is appreciated that during the sequential cycles of optimization ofsub-beam A, the relative phases of the remainder of the sub-beams arevaried as usual, each at a phase varying rate that far exceeds the noisesampling rate at which the noise in sub-beam A is taken intoconsideration.

As seen further in the case of sub-beam B, and appreciated most clearlyfrom consideration of an enlargement 492, the thicker trace duringoptimization of channel B represents the pattern of variation inrelative phase of sub-beam B, as would be applied by phase controlsub-system 430 in the absence of any noise correction. This trace may betermed B_(uncorrected). The thinner trace during optimization of channelB represents the actual relative phase of sub-beam B as modified by thenoise correction algorithm in order to find the optimum phase noisecorrection. This trace may be termed B_(corrected). The modifiedrelative phase of B_(corrected) is shifted with respect to thenon-modified relative phase of B_(uncorrected) by a different Δφ_(B)over five cycles of optimization sub-beam B. The intensity 486 measuredat detector 450 varies over these five cycles of optimization sub-beam Bdue to the deliberate change in relative phase shift.

Following these five cycles of sub-beam B, the algorithm ascertains themaximum intensity and finds the phase change Δφ_(B) that produces themaximum intensity. In this case, the maximum intensity is seen to beIAB_(max), produced by the fourth phase shift Δφ_(B). The phase changeapplied to relative phase variation of sub-beam B is then fixed at thefourth phase shift Δφ_(B) for subsequent cycles and the algorithmproceeds to optimize sub-beam C.

It is appreciated that during the five cycles of optimization ofsub-beam B, the relative phases of the remainder of the sub-beams arevaried as usual, each at a phase varying rate that far exceeds the noisesampling rate at which the noise in sub-beam B is taken intoconsideration.

A similar optimization process is preferably implemented for sub-beam C,in which a phase change Δφ_(C) is applied over several cycles in orderto optimize the output beam intensity and correct for intensitydegradation thereof due to phase noise in sub-beam C.

Detector 450 may operate continuously in order to continuously optimizethe relative phases of the sub-beams and correct for phase noisetherein. However, due to a finite response time of detector 450,detector 450 only takes into consideration the noise in reference beam470 at intermittent times, at a relatively slow noise sampling rate. Thenoise sampling rate is preferably but not necessarily predetermined. Thenoise sampling rate may alternatively be random.

It is appreciated that the particular parameters of the noise correctionalgorithm depicted in graph 480 are exemplary only and may be readilymodified, as will be understood by one skilled in the art. For example,the phase shift Δφ may be optimized over a greater or fewer number ofcycles than illustrated herein, each sub-beam may be fully optimizedeach time the sub-beam passes over detector 450 or several sub-beams orall of the sub-beams may be optimized during each cycle in which thefar-field intensity pattern passes over detector 450. Furthermore,non-sequential noise correction optimization algorithms mayalternatively be implemented, including, but not limited to, Stochasticparallel gradient descent optimization algorithms.

The use of dynamically shaped, noise corrected optical phased arrayoutput beams for laser welding is highly advantageous and enables rapidbeam steering, fast power modulation, fast beam focusing and beam shapetailoring. Both the speed and quality with which a material may be cutare improved using dynamically shaped, noise corrected optical phasearray output in comparison to conventional laser cutting methods. It isappreciated that but for the provision of noise correction, inaccordance with preferred embodiments of the present invention, theshape and position of the optical phased array output beam would bedegraded, thereby degrading the quality, speed and precision of thelaser cutting process.

In order to maintain output beam intensity as the far-field intensitypattern of the beam moves, as is advantageous in certain laser cuttingapplications, movement of the output beam may be controlled such thatthe beam spends more time at lower-intensity positions so as tocompensate for reduced power delivery thereat. Additionally oralternatively, an intensity profile mask such as an ND filter may beapplied to the output beam in order to modify the intensity thereof.

Reference is now made to FIGS. 5A-5G, which are simplified illustrationsof possible far-field motion of an output of an optical phased arraylaser system of the types illustrated in FIGS. 1A-4C.

As detailed hereinabove, the use of dynamically shaped, noise correctedoptical phased array output beams in various laser applications,including but not limited to laser cutting, laser additivemanufacturing, laser welding and laser free-space optical communication,is highly advantageous and enables rapid beam steering, fast powermodulation, fast beam focusing and beam shape tailoring. Exemplaryfar-field patterns illustrating rapid beam steering in accordance withembodiments of the present invention are shown in FIGS. 5A and 5B. Thesebeam steering patterns may be provided in combination with and so as tocompliment mechanical spatial modulation of the beam, such as mechanicalbeam steering. Mechanical beam steering may be due to motion provided bypositioning table 104 shown in FIG. 1A; due to mirror scanning, such asin an additive manufacturing system of the type shown in FIG. 2A; due tomechanical motion between laser system 300 and receiver 303 shown inFIG. 3A; due to motion provide by robot 404 shown in FIG. 4A, or due toany other source of mechanical motion.

The mechanical motion may be desired or undesired motion. Preferably,the far-field rapid beam steering provided by embodiments of the presentinvention compliments the mechanical motion so as to achieve the desiredcombined beam motion. The desired combined motion may be faster and/ormore precise than would be produced as a result of mechanical beammodulation alone.

As seen in FIG. 5A, dynamically shaped, noise corrected optical phasedarray output beams may exhibit rapid multipoint jumping, as illustratedby first beam paths 502, which rapid multipoint jumping compliments beammotion due to mechanical scanning, represented by a second beam path504.

By way of example, such multipoint jumping may be advantageous inmaterial processing, wherein time is taken for energy to be absorbed ateach point of the material being processed. Multipoint jumping allowsthe beam to jump between points, returning to each point multiple times,thus facilitating the processing of many points in parallel. Further byway of example, such multipoint jumping may be advantageous incommunication systems by allowing transmission to multiple locations inparallel.

As seen in FIG. 5B, the use of dynamically shaped, noise correctedoptical phased array output beams also facilitates rapid scanning, asillustrated by a third beam path 506, which rapid scanning complimentsbeam motion due to mechanical scanning represented by a fourth beam path508. Such rapid scanning facilitates continuous, smooth mechanical beammotion, fine features of which may be provided by far-field dynamicshaping in accordance with embodiments of the present invention.Furthermore, dynamic noise corrected far field modulation may beprovided in combination with mechanical beam motion in order to correctinaccuracies that may be present in the mechanically modulated beampatterns.

An exemplary far field beam pattern illustrating electro-optical beamwobble in accordance with preferred embodiments of the present inventionis shown in FIG. 5C. As seen in FIG. 5C, the dynamically shaped, noisecorrected optical phased array output beam is controlled so as toexhibit a rapid beam wobble 510 along a direction of beam motion 512,particularly useful, for example, in a laser welding system such as thatillustrated in FIG. 4A.

Exemplary far-field beam patterns illustrating dynamic modification ofdepth of focus in accordance with preferred embodiments of the presentinvention are shown in FIGS. 5D-5F. As seen in FIGS. 5D-5F, the depth ofthe beam focus may be dynamically changed by systems of the presentinvention, allowing variable beam focal length for scanning (FIG. 5E)and for deep cutting (FIGS. 5D and 5F), particularly useful, forexample, in cutting, additive manufacturing and welding systems of thetypes illustrated in FIGS. 1A, 2A and 4A.

Exemplary far-field beam patterns illustrating dynamic beam shaping inaccordance with preferred embodiments of the present invention are shownin FIG. 5G. As seen in FIG. 5G, the shape of the beam may be dynamicallychanged to create a desired beam shape output. This may be particularlyuseful, for example, in cutting, additive manufacturing and weldingsystems of the types illustrated in FIGS. 1A, 2A and 4A, as well as inother contexts. As is well known in the art, the quality and speed oflaser cutting, welding and 3D printing are typically influenced by beamsize and shape. The present invention allows dynamic adaptation of thebeam to the optimum shape at any point.

It is appreciated that the various far-field beam motion patternsillustrated in FIGS. 5A-5G are all preferably produced by systems of thepresent invention using digital electronic controls and withoutrequiring any moving parts.

Reference is now made to FIG. 6 , which is a simplified schematicillustration of an optical phased array laser system including multipledetectors and corresponding multiple closely spaced optical pathways,constructed and operative in accordance with a preferred embodiment ofthe present invention.

As seen in FIG. 6 , there is provided an optical phased array (OPA)laser 600. OPA laser 600 may be generally of the type shown in any ofFIGS. 1A-4C and preferably includes a seed laser 612 and a laser beamsplitting and combining subsystem 614. Splitting and combining subsystem614 preferably receives an output laser beam from seed laser 612 andsplits the output laser beam into a plurality of sub-beams along acorresponding plurality of channels 616. Here, by way of example only,an output from seed laser 612 is shown to be split into four sub-beamsalong four channels 616 although it is appreciated that splitting andcombining subsystem 614 may include a fewer or greater number ofchannels along which the output of seed laser 612 is split, andtypically may include a far greater number of channels such as 32 ormore channels.

The relative phase of each sub-beam may be individually modulated by aphase modulator 618, preferably located along each of channels 616. Eachphase modulated sub-beam produced by the splitting and subsequent phasemodulation of the output of seed laser 612 preferably propagates towardsa collimating lens 619. The individually collimated, phase modulatedsub-beams are subsequently combined, for example at a focal lens 620, toform an output beam 622.

Splitting and combining subsystem 614 may also provide laseramplification of the sub-beams, preferably following the splitting ofthe output beam of seed laser 612 into sub-beams and prior to thecombining of the sub-beams to form output beam 622. Here, by way ofexample, splitting and combining subsystem 614 is shown to include aplurality of optical amplifiers 624 located along corresponding ones ofchannels 616 for amplifying each sub-beam. It is appreciated, however,that such amplification is optional and may be omitted, depending on thepower output specifications of OPA laser 600.

The phase of output beam 622, and hence the position and shape of thefar-field intensity pattern thereof, is controlled, at least in part, bythe relative phases of the constituent sub-beams combined to form outputbeam 622. As described hereinabove with reference to FIGS. 1A-5G, inmany applications, such as laser cutting, laser welding, laser additivemanufacturing and optical free space communications, it is desirable todynamically move and shape the far-field intensity pattern of the outputbeam. This may be achieved in laser system 600 by laser splitting andcombining subsystem 614 dynamically varying the relative phases of theindividual sub-beams and thereby varying the phase of the combined laseroutput 622 so as dynamically to control the position and shape of thefar-field intensity pattern thereof.

The relative phases of the sub-beams are preferably predetermined inaccordance with the desired laser output pattern. Particularlypreferably, the varying relative phases are applied by a phase controlsubsystem 630. Phase control subsystem 630 preferably forms a part of acontrol electronics module 632 in OPA laser 600 and preferably controlseach phase modulator 618 so as to dynamically modulate the relativephases of the sub-beams along channels 616, as described hereinabovewith reference to phase control subsystem 130, 230, 330, 430 of FIGS.1A, 2A, 3A and 4A respectively.

Due to noise inherent in OPA system 600, output beam 622 has noise.Noise in output beam 622 is typically phase noise created by thermal ormechanical effects and/or by the amplification process in the case thatoptical amplifiers 624 are present in OPA system 600. OPA system 600preferably includes a noise cancellation subsystem 640 operative toprovide a noise cancellation phase correction output in order to cancelout the noise in output beam 622 in a manner detailed henceforth.

Particularly preferably, noise cancellation subsystem 640 employs analgorithm to sense and correct phase noise in the combined laser output,preferably, although not necessarily, of the type described hereinabovewith reference to FIGS. 1A-4C. The noise cancellation phase correctionoutput is preferably provided by noise cancellation subsystem 640 tophase modulators 618 so as to correct phase noise in output beam 622 andthus avoid distortion of the shape and position of the far fieldintensity pattern of output beam 622 that would otherwise be caused bythe noise. Noise cancellation subsystem 640 may be included in controlelectronics module 632.

In order to facilitate application of phase variation and noisecorrection to output beam 622, a portion of the output of OPA laser 600is preferably extracted and directed towards a plurality of detectors650. The extracted portion of the output beam preferably functions as areference beam, based on characteristics of which the required noisecorrection and/or phase variation may be calculated.

In accordance with a preferred embodiment of the present invention,plurality of sub-beams along channels 616 are directed towards a beamsplitter 660. Beam splitter 660 preferably splits each sub-beam into atransmitted portion 662 and a reflected portion 664 in accordance with apredetermined ratio. For example, beam splitter 660 may split eachsub-beam with a 99.9% transmitted: 0.01% reflected ratio.

The transmitted portion 662 of the sub-beams preferably propagatestowards focal lens 620, at which focal lens 620 the sub-beams arecombined to form output beam 622 having a far-field intensity pattern666. The reflected portion 664 of the sub-beams is preferably reflectedtowards an additional focal lens 668, at which additional focal lens 668the sub-beams are combined to form an output reference beam 670 having afar-field intensity pattern 672 incident on a surface of one or more ofplurality of detectors 650.

As described hereinabove with reference to FIGS. 1A-4C, the noisecancellation phase correction output is preferably provided based ontaking into consideration noise measured at detectors 650 at a noisesampling rate. The output beam 622 is controlled in such a way that thefar-field intensity pattern 672 is incident upon detectors 650 duringthe course of the dynamic changes to the shape and position of outputand reference far-field intensity patterns 666, 672 at a rate that isequal to or higher than the required noise sampling rate. The noise inreference beam 670 is taken into consideration during those intermittenttimes at which the far-field intensity pattern 672 is returned todetectors 650.

At time interstices between the intermittent times at which far-fieldintensity pattern 672 is incident upon detectors 650, the phase of thecombined output beams 622, 670 is varied in order to dynamically changethe shape and position of the far-field intensity pattern thereof. Thecombined laser output is varied at a phase varying rate which exceedsthe noise sampling rate, in order to rapidly change the phase and henceshape and position of the far-field intensity pattern. The noisecancellation and phase variation are thus preferably provided atmutually different times and rates.

The use of a plurality of detectors 650, rather than a single detector,has been found to be highly advantageous in certain embodiments of thepresent invention, giving rise to various advantages detailedhenceforth. However, in the case of the focal length of additional focallens 668 being relatively short, as is desirable in order for system 600to be formed in a compact manner, ones of plurality of detectors 650would preferably be required to be positioned very close to one another.The desirable inter-detector spacing may be of the order of severalmicrons. Such a high spatial density arrangement of detectors 650 istypically impractical, particularly in the case of conventionaldetectors having dimensions far greater than the preferredinter-detector spacing.

In order to allow high spatial density sampling of far-field intensitypattern 672 by plurality of detectors 650, OPA system 600 preferablyincludes a plurality of optical pathways, here embodied by way ofexample as a plurality of optical fibers 680, correspondingly coupled toplurality of detectors 650. Reference beam 670 preferably enters one ormore of a plurality of open ends 682 of optical fibers 680 and travelstherealong to corresponding ones of detectors 650. Plurality of ends 682of plurality of optical fibers 680 is preferably arranged so as to havea spatial density greater than a spatial density of plurality ofdetectors 650, meaning that the spacing between open ends 682 ofadjacent ones of optical fibers 680 is smaller than the spacing betweencorresponding adjacent ones of detectors 650. This allows detectors 650to detect far-field intensity pattern 672 at closely spaced intervalstherealong, without detectors 650 being required to be themselvesphysically located at those closely spaced positions at which thefar-field intensity pattern 672 is sampled.

By way of example, ends 682 of optical fibers 680 may be interspaced bya distance of several microns, whereas detectors 650 coupled tocorresponding ones of optical fibers 680 may be interspaced by adistance of several millimeters. It is appreciated that such anarrangement allows the use of conventional detectors in system 600, andobviates the need for expensive and complex miniaturized detectionsystems.

The inclusion of a plurality of detectors 650, effectively closelyspaced as facilitated by the actual physical close spacing of ends 682of optical fibers 680, has been found to be highly advantageous inpreferred embodiments of the present invention. In particular, the useof a plurality of detectors 650 rather than only a single detector 150,as shown in FIGS. 1A, 2A, 3A and 4A, allows the far-field intensitypattern 672 to be sampled at a plurality of locations rather than atonly a single location. This facilitates more efficient and/or morefrequent noise correction during the dynamic variation of output beam622.

It is appreciated that the plurality of closely spaced optical pathwaysis not limited to being embodied as a plurality of optical fibers 680having ends 682 very closely interspaced, with an inter-fiber endspacing of less than the inter-detector spacing of detectors 650.Rather, the scope of the present invention extends to include anysuitable plurality of optical pathways that may deliver therealongfar-field intensity reference pattern 672 to plurality of detectors 650,and may be arranged with a sufficiently great spatial density.

By way of example, the plurality of closely spaced optical pathways maybe embodied as a plurality of lenses 780 as illustrated in FIG. 7 .Plurality of lenses 780 may be very closely spaced so as to focusportions of far-field intensity reference pattern 672 towards pluralityof less closely spaced detectors 650. Further by way of example, theplurality of closely spaced optical pathways may be embodied as aplurality of mirrors 880 operating in cooperation with a correspondingplurality of lenses 882 as illustrated in FIG. 8 . Plurality of mirrors880 may be very closely spaced so as to reflect portions of far-fieldintensity reference pattern 672 towards plurality of less closely spaceddetectors 650.

It is appreciated that an OPA laser system of the type shown in any ofFIGS. 6-8 , including multiple detectors, may be incorporated in an OPAlaser system of the type shown in any of FIGS. 1A, 2A, 3A and 4A inorder to provide more efficient and/or more frequent noise correction tothe phase-varied output thereof.

Reference is now made to FIG. 9 , which is a simplified schematicillustration of an optical phased array laser system including adetector mask configured in accordance with an exemplary laser beamtrajectory, constructed and operative in accordance with a preferredembodiment of the present invention.

As seen in FIG. 9 , there is provided an optical phased array (OPA)laser 900. OPA laser 900 may generally resemble OPA laser 600 of FIG. 6in relevant aspects thereof, with the exception of the detectorarrangement employed therein. Whereas OPA laser 600 preferably employsmultiple detectors receiving an output beam by way of correspondingmultiple closely spaced optical pathways, OPA laser 900 does notnecessarily employ more than one detector.

It is particular feature of a preferred embodiment of the presentinvention illustrated in FIG. 9 that OPA laser 900 preferably includesan optical mask 980 having at least one transmissive region 982 forproviding therethrough output reference beam 670 to at least onedetector 650, here illustrated to comprise a single detector 650.Optical mask 980 is preferably an optically opaque element transmissiveto beam 670 only in transmissive region 982. Here, by way of example,transmissive region 982 is shown to be formed as a star-shapedtransmissive path, configured in accordance with a star-shapedtrajectory of output and reference far-field intensity patterns 666,672.

Output reference beam 670 is preferably transmitted through transmissiveregion 982 and focused on detector 650 by way of a focusing subsystem,here embodied by way of example, as a focusing lens 990. A noisecancellation phase correction output is preferably provided by noisecancellation subsystem 630 based on taking into consideration theintensity of far-field intensity pattern 672 focused and incident upondetector 650.

More specifically, the phases of output and reference beams 622, 670 arepreferably dynamically varied by phase control subsystem 630 so as tocause output and reference beams 622 and 670 to traverse a predeterminedtrajectory, such as a star-shaped trajectory corresponding to the shapeof star-shaped transmissive region 982. In the absence of noise in OPAlaser 900, the trajectory traversed by output and reference beams 622and 670 would at least nearly exactly correspond to the shape oftransmissive region 982, such that an intensity of far-field intensitypattern 672 as detected by detector 650 would be a maximal, non-degradedintensity. However, due to the presence of noise in output and referencebeams 622 and 670, a trajectory and shape of far-field intensity pattern672 may somewhat deviate from the shape of transmissive region 982, suchthat a portion of reference beam 670 is incident upon opaque regions ofmask 980 rather than on transmissive region 982, and thus nottransmitted to detector 650 through transmissive region 982. In such acase, the intensity of far-field intensity pattern 672 as detected bydetector 650 is lower than the maximal intensity that would be detectedin the absence of noise.

The degradation in intensity of far-field intensity pattern 672 asmeasured by detector 650 is thus preferably indicative of thenoise-resultant distortion of the trajectory of output and referencebeams 622, 670 and thereby may be used to derive the required noisecancellation phase correction output, to be applied by noisecancellation subsystem 640.

It is appreciated that the above-described arrangement of detector 650positioned behind mask 980 allows only a single detector 650 to beemployed in order to sense the output intensity of reference beam 670along a trajectory thereof, based on which a noise cancellation phasecorrection output may be applied. This is contrast to alternativedetector arrangements not including mask 980, such as those describedhereinabove with reference to FIGS. 6-8 , in which multiple detectorsmay be employed in order to provide sufficiently efficient and/orfrequent noise correction during the dynamic variation of output beam622.

In addition to the variation of intensity of reference beam 670 asmeasured by detector 650 due to the distortion of the beam trajectorydue to noise, the intensity of reference beam 670 typically may varyalong the trajectory thereof, due to inherent intensity variations infar-field intensity pattern 672. This may complicate the noisecorrection feedback provided by detector 650, since variations inintensity of reference beam 670 may be attributable to noise or toinherent intensity variations not related to noise.

In order to improve the reliability of the noise correction feedbackprovided by detector 650, transmissive region 982 of mask 980 may beprovided with regions of varying transparency, the transparency levelsof which are set so as to compensate for inherent intensity variationsin reference beam 670 along the trajectory thereof.

A highly simplified representation of transmissive region 982 of mask980 having non-uniform transparency is shown in FIG. 10 . As seen inFIG. 10 , a first portion of transmissive region 982 defined between afirst point P1 and a second point P2 thereof may have a firsttransparency T1; a second portion of transmissive region 982 definedbetween second point P2 and a third point P3 may have a secondtransparency T2, different from first transparency T1; a third portionof transmissive region 982 defined between third point P3 and a fourthpoint P4 may have first transparency T1; a fourth portion oftransmissive region 982 defined between fourth point P4 and a fifthpoint P5 may have a third transparency T3, different from first andsecond transparencies T1 and T2; and a fifth point of transmissiveregion 982 defined between fifth point P5 and first point P1 may havesecond transparency T2.

It is appreciated that various portions of transmissive region 982 mayhave discretely differing transparency values or that the transparencyof transmissive region 982 may gradually vary in a gradated way acrossvarious portions thereof, in accordance with the intensity compensationrequirement of far-field intensity pattern 672.

Preferably, although not necessarily, mask 980 is an electronicallymodulated device such as an LCD screen or similar device. Properties oftransmissive region 982 thus may be readily electronically modified inaccordance with the output characteristics of reference beam 670.

It is appreciated that the particular shape of transmissive region 982illustrated in FIGS. 9 and 10 is exemplary only and that transmissiveregion 982 may be configured in accordance with any trajectory of outputand reference far-field intensity patterns 666 and 672. Additionally, itis appreciated that transmissive region 982 may include more than onetransmissive region. In such a case, a single detector 650 may be usedto receive light from all transmissive regions, or a correspondingnumber of detectors may be positioned with respect to each transmissiveregion.

Furthermore, it is appreciated that transmissive region 982 mayadditionally or alternatively be configured in accordance with a shapeof output and reference far-field intensity patterns 666 and 672, ratherthan a trajectory thereof, as is detailed with reference to FIGS. 11 and12 .

Reference is now made to FIG. 11 , which is simplified schematicillustration of an optical phased array laser system including adetector mask configured in accordance with an exemplary laser beamshape, constructed and operative in accordance with another preferredembodiment of the present invention.

As seen in FIG. 11 , a system 1100 generally resembling system 900 inrelevant aspects thereof may include an optical mask 1180 having atleast one transmissive region 1182, replacing optical mask 980 of FIGS.9 and 10 . Optical mask 1180 may resemble optical mask 980 in allrelevant aspects thereof, with the exception of transmissive region 1182being configured in accordance with a shape of reference beam 670 ratherthan a trajectory thereof. Here, by way of example, transmissive region1182 is shown to be a bow-tie shaped transmissive region, configured inaccordance with a bow-tie shaped output and reference far-fieldintensity pattern 666 and 672.

Transmissive region 1182 may have non-uniform transparency, a highlysimplified representation of which is illustrated in FIG. 12 . As seenin FIG. 12 , a first portion of transmissive region 1182 may have afirst transparency T1 and a second portion of transmissive region 1182may have a second transparency T2, different from first transparency T1.As detailed hereinabove with reference to FIG. 10 , various levels oftransparency of transmissive region 1182 may be employed in order tocompensate for inherent intensity variation in output beam 670 and thusimprove the noise correction output provided based on the intensitydetected at detector 650.

It is appreciated that transmissive regions 982 and 1182 of masks 980and 1180 respectively may additionally or alternatively be embodied asreflective regions, reflecting therefrom output reference beam 670towards detector 650. In such an arrangement, appropriate modificationsand/or additions to focusing subsystem, here embodied by way of exampleas focusing lens 990, would be required, in order to direct outputreference beam 670 from reflective region 982, 1182 onto a surface ofdetector 650. The reflective regions of masks 980 and 1180 may haveuniform reflectivity. Alternatively, reflective regions of masks 980 and1180 may have non-uniform reflectivity, in order to compensate forinherent intensity variations in output reference beam 670, as describedhereinabove.

In the case that masks 980 and 1180 include a reflective region, masks980 and 1180 may be embodied as an electrically modulated device such asa digital micromirror device (DMD) or other similar device.

It is appreciated that an OPA laser system of the type shown in any ofFIGS. 9-12 , including at least one detector receiving an outputreference beam via a transmissive or reflective optical mask, may beincorporated in an OPA laser system of the type shown in any of FIGS.1A, 2A, 3A and 4A in order to provide more efficient noise correction tothe phase-varied output thereof.

Reference is now made to FIG. 13 , which is a simplified schematicillustration of an optical phased array laser system includingvoltage-phase correlating functionality, constructed and operative inaccordance with a preferred embodiment of the present invention.

As seen in FIG. 13 , there is provided an OPA laser system 1300. OPAlaser 1300 may be of a type generally resembling OPA lasers 100, 200,300, 400 described hereinabove with reference to FIGS. 1A-4C. OPA laser1300 preferably comprises a seed laser 1312 and a laser beam splittingand combining subsystem 1314. Splitting and combining subsystem 1314preferably receives an output laser beam from seed laser 1312 and splitsthe output laser beam into a plurality of sub-beams along acorresponding plurality of channels 1316.

The relative phase of each sub-beam may be individually modulated by aphase modulator 1318, preferably located along each of channels 1316.Each phase modulated sub-beam produced by the splitting and subsequentphase modulation of the output of seed laser 1312 preferably propagatestowards a collimating lens 1319. The individually collimated, phasemodulated sub-beams are subsequently combined, for example at a focalplane of a lens 1320, to form an output beam 1322.

Splitting and combining subsystem 1314 may also provide laseramplification of the sub-beams, preferably following the splitting ofthe output beam of seed laser 1312 into sub-beams and prior to thecombining of the sub-beams to form output beam 1322. Here, by way ofexample, splitting and combining subsystem 1314 is shown to include aplurality of optical amplifiers 1324 located along corresponding ones ofchannels 1316 for amplifying each sub-beam. It is appreciated, however,that such amplification is optional and may be omitted, depending on thepower output specifications of OPA laser 1300.

The phase of output beam 1322, and hence the position and shape of thefar-field intensity pattern thereof, is controlled, at least in part, bythe relative phases of the constituent sub-beams combined to form outputbeam 1322. In many applications, such as laser cutting, laser welding,free-space optical communications and laser additive manufacturingdescribed hereinabove, it is desirable to dynamically move and shape thefar-field intensity pattern of the output beam. As described hereinabovewith reference to FIGS. 1A-4C, dynamic variation of parameters of theoutput beam may be achieved by dynamically varying the relative phasesof the individual sub-beams along channels 1316 and thereby varying thephase of the combined laser output 1322 so as to dynamically control theposition and shape of the far-field intensity pattern thereof.

The relative phases of the sub-beams are preferably predetermined inaccordance with the desired laser output pattern. Particularlypreferably, the varying relative phases are applied by a phasemodulation control module 1330. Phase modulation control module 1330preferably provides a voltage to phase modulators 1318 in order forphase modulators 1318 to produce the desired phase modulation ofsub-beams along channels 1316. It is appreciated that phase modulationcontrol module 1330 in combination with phase modulators 1318 forms aparticularly preferred embodiment of a phase modulation subsystem 1332,which phase modulation subsystem 1332 is preferably operative to vary aphase of combined laser output 1322.

In order to facilitate application of phase variation to output beam1322, a portion of the output of OPA laser 1300 is preferably extractedand directed towards at least one detector 1350. The extracted portionof the output beam preferably functions as a reference beam, based oncharacteristics of which the required phase variation may be calculated.In the embodiment shown in FIG. 13 , plurality of sub-beams alongchannels 1316 are directed towards a beam splitter 1360. Beam splitter1360 preferably splits each sub-beam into a transmitted portion 1362 anda reflected portion 1364 in accordance with a predetermined ratio. Forexample, beam splitter 1360 may split each sub-beam with a 99.9%transmitted: 0.01% reflected ratio.

The transmitted portion 1362 of the sub-beams preferably propagatestowards focal lens 1320, at which focal lens 1320 the sub-beams arecombined to form output beam 1322 having a far-field intensity pattern1366. The reflected portion 1364 of the sub-beams preferably propagatestowards an additional focal lens 1368, at which additional focal lens1368 the sub-beams are combined to form an additional reference beam1370 having a far-field intensity pattern 1372 incident on a surface ofdetector 1350.

Detector 1350 preferably samples the far-field intensity pattern 1372incident thereon. It is appreciated that although detector 1350 isillustrated in FIG. 13 as being embodied as a single detector directlyreceiving far-field intensity pattern 1372 thereupon, multiple detectorsmay alternatively be employed in accordance with any of the multipledetector arrangements illustrated in any of FIGS. 6-8 . Alternatively, asingle detector such as detector 1350 may be employed in conjunctionwith an optical mask, in accordance with any of the arrangementsillustrated in any of FIGS. 9-12 .

Detector 1350, in cooperation with phase modulation subsystem 1332, thenpreferably optimizes the relative phases of the sub-beams in order toachieve a desired far-field intensity pattern 1372 and correspondingfar-field intensity pattern 1366. Various algorithms suitable for phaseoptimization include sequential or non-sequential optimizationalgorithms, including the phase optimization regime describedhereinabove with reference to FIGS. 1A-4C.

In operation of phase modulation subsystem 1332, phase modulationcontrol module 1330 preferably applies a voltage to each of phasemodulators 1318 and phase modulators 1318 consequently produce a phasemodulating output corresponding to the voltage applied. It isappreciated that in order for phase modulators 1318 to produce therequired phase shift so as to dynamically shape far-field intensitypattern 1366 in accordance with a predetermined pattern, phasemodulation control module 1330 must apply to each phase modulator 1318exactly that voltage corresponding to the specific phase modulationoutput required to be produced by each phase modulator 1318.

In order to ensure that the voltage applied by phase modulation controlmodule 1330 to phase modulators 1318 produces the required and intendedphase modulating output by phase modulators 1318, OPA laser 1300preferably includes a voltage-to-phase correlation subsystem 1380.Voltage-to-phase correlation subsystem 1380 is preferably operative tocorrelate a voltage applied to phase modulation subsystem 1332 to aphase modulating output produced by phase modulation subsystem 1332 andmore specifically by phase modulators 1318 thereof.

Furthermore, voltage-to-phase correlation subsystem 1380 is preferablyoperative to provide a voltage-to-phase correlation output useful incalibrating phase modulation subsystem 1332. Preferably,voltage-to-phase correlation subsystem performs the correlating betweenthe voltage and phase modulating output periodically during the courseof varying of the phase of combined laser output 1322.

It is appreciated that the inclusion of a correlation and calibrationsubsystem such as voltage-to-phase correlation subsystem 1380 in OPAlaser 1300 is highly advantageous since it ensures that the voltagesbeing applied to phase modulators 1318 are indeed those voltagesrequired to produce the desired phase shift of output beam 1322 andhence shape of far-field intensity pattern 1366. This is particularlyimportant given that phase modulators suitable for use in preferredembodiments of the present invention are typically highly sensitivedevices, different ones of which typically exhibit differentvoltage-phase relationships. Furthermore, the voltage-phase relationshipof an individual phase modulator is not constant but rather may varyover time and in response to operating conditions.

It is appreciated that the phase modulation and calibration provided byphase modulation control module 1330 and voltage-phase correlationcontrol module 1380 respectively, are preferably, although notnecessarily, performed in coordination with the application of noisecorrection to the output of OPA laser 1300 in the case that the outputof laser 1300 has noise. In this case, phase modulation control module1330 and voltage-phase correlation control module 1380 may be consideredto combinedly form a particularly preferred embodiment of a phasecontrol subsystem such as phase control subsystem 130 (FIG. 1A), 230(FIG. 2A), 330 (FIG. 3A) and 430 (FIG. 4A).

An exemplary voltage-phase correlation and calibration regime suitablefor use in the present invention is illustrated in a flow chart 1400 inFIG. 14 . It is appreciated, however, that the specific steps of flowchart 1400 are exemplary only and that voltage-phase correlationsubsystem 1380 may be implemented as any suitable subsystem within OPAlaser 1300 capable of calibrating phase modulation subsystem 1332periodically during the phase variation of output beam 1322.Furthermore, it is appreciated that the various steps illustrated inflow chart 1400 are not necessarily performed in the order shown anddescribed and that various ones of the steps may be omitted, or may besupplemented by additional or alternative steps, as will be apparent toone skilled in the art.

As seen at a first step 1402, phase modulation control module 1330preferably applies a voltage to phase modulators 1318 in order toproduce the desired phase shift of sub-beams along channels 1316. Thefar-field intensity pattern of the reference output beam 1372 is thenmeasured at detector 1350, as seen at a second step 1404. The requiredphase shift of the sub-beams is then ascertained and a voltage againapplied to phase modulators 1318. The application of a voltage at firststep 1402 and measurement of the reference output beam 1372 at secondstep 1404 may be periodically repeated a large number of times at agiven repetition rate. By way of example only, first and second stepsmay be repeated 20 times at a rate of 1 million times per second.

Following the repetition of first and second steps 1402, 1404 apredetermined number of times, such as 20 times, voltage-to-phasecorrelation subsystem 1380 may be activated. As seen a third step 1406,a voltage intended to produce a phase shift of 2π is preferably appliedto one phase modulator 1318. As seen at a fourth step 1408, theintensity of far-field intensity pattern 1372 is then measured,preferably at detector 1350.

The phase shift of far-field intensity pattern 1372 is then checked at afifth step 1410 to ascertain whether the phase shift is zero. It isunderstood that in the case that the voltage applied at third step 1406is indeed that voltage producing a phase shift of 2π, the phase shift ofbeam 1322 would be zero and the intensity of far-field intensity pattern1372 would thus not change in response to the voltage applied. In thiscase, the phase modulator 1318 to which the a phase shift was applied atthird step 1406 is found to be correctly calibrated and no additionalcalibration of the particular phase modulator 1318 is required.

It is further understood that in the case that the voltage applied atthird step 1406 does not produce a phase shift of 2π, the phase shift ofbeam 1322 would be non-zero and the intensity of far-field intensitypattern 1372 would thus change in response to the voltage applied, asfound to be the case at a seventh step 1414. In this case, therelationship between the applied voltage and the resultant phase shiftis preferably derived at seventh step 1414. Phase modulator 1318 ispreferably then calibrated in accordance with the voltage-phaserelationship derived at seventh step 1414, as seen at an eighth step1416.

As seen at a query 1418, following the calibration of a particular phasemodulator 1318 at eighth calibration step 1416 or ascertainment ofproper calibration of a particular phase modulator 1318 at fifth step1410, voltage-to-phase correlation subsystem 1380 preferably checkswhether a predetermined number of phase modulators 1318 has beencalibrated and proceeds to calibrate the next phase modulator ifnecessary, as seen at a ninth step 1420. Voltage-to-phase correlationsubsystem 1380 may successively calibrate all of phase modulators 1318included in system 1300 or may successively calibrate a predeterminednumber of phase modulators 1318, such as N phase modulators 1318. Oncethe predetermined number of phase modulators 1318 has been calibrated,subsystem 1380 is preferably deactivated and phase variation of outputbeam 1322 is resumed at step 1402.

It is understood that the frequency at which voltage-to-phasecorrelation subsystem 1380 is activated is preferably significantlylower than the frequency at which phase variation of output beam 1322 isperformed. By way of example phase variation of output beam 1322 may beperformed 1 million times per second while voltage-to-phase correlationmay be activated 1 time per second.

Furthermore, it is understood that although flow chart 1400 does notinclude steps for noise correction, such noise correction may be appliedduring the course of the phase shifting of the sub-beams contributing tooutput beam 1322, as described hereinabove with reference to FIGS.1A-4C.

Reference is now made to FIG. 15 , which is a simplified schematic planview illustration of an optical phased array laser system includingscaled phase modification of dynamic beams, constructed and operative inaccordance with an additional preferred embodiment of the presentinvention.

As seen in FIG. 15 , there is provided an optical phased array (OPA)laser system 1500, which OPA laser 1500 may be of a type generallydescribed hereinabove with reference to FIGS. 1A-4C. OPA laser 1500preferably comprises a seed laser 1512 and a laser beam splitting andcombining subsystem 1514. Splitting and combining subsystem 1514preferably receives an output laser beam from seed laser 1512 and splitsthe output laser beam into a plurality of sub-beams along acorresponding plurality of channels 1516. Here, by way of example only,an output from seed laser 1512 may be split into a 4×4 matrix of 16sub-beams along 16 corresponding channels 1516, four of which sub-beamsand channels 1516 are seen in the top view of OPA laser 1500 in FIG. 15. It is appreciated, however, that splitting and combining subsystem1514 may include a fewer or greater number of channels along which theoutput of seed laser 1512 is split, and typically may include a fargreater number of channels such as 32 or more channels.

The relative phase of each sub-beam may be individually modulated by aphase modulator 1518, preferably located along each of channels 1516.Each phase modulated sub-beam produced by the splitting and subsequentphase modulation of the output of seed laser 1512 preferably propagatestowards a collimating lens 1519. The individually collimated, phasemodulated sub-beams are subsequently combined, for example at a focalplane of lens 1520, to form an output beam 1522.

Splitting and combining subsystem 1514 may also provide laseramplification of the sub-beams, preferably following the splitting ofthe output beam of seed laser 1512 into sub-beams and prior to thecombining of the sub-beams to form output beam 1522. Here, by way ofexample, splitting and combining subsystem 1514 is shown to include aplurality of optical amplifiers 1524 located along corresponding ones ofchannels 1516 for amplifying each sub-beam. It is appreciated, however,that such amplification is optional and may be omitted, depending on thepower output specifications of OPA laser 1500.

The phase of output beam 1522, and hence the position and shape of thefar-field intensity pattern thereof, is controlled, at least in part, bythe relative phases of the constituent sub-beams combined to form outputbeam 1522. In many applications, such as laser cutting, laser welding,free-space optical communications and laser additive manufacturing, asdescribed hereinabove, it is desirable to dynamically move and shape thefar-field intensity pattern of the output beam. As described hereinabovewith reference to FIGS. 1A-4C, dynamic variation of parameters of theoutput beam may be achieved by dynamically varying the relative phasesof the individual sub-beams along channels 1516 and thereby varying thephase of the combined laser output 1522 so as to dynamically control theposition and shape of the far-field intensity pattern thereof.

In the case of OPA laser 1500 including a large number of individualsub-beams, phase measurement and corresponding phase modification ofeach sub-beam with respect to the phases of all of the other ones of thesub-beams, may be challenging due to the large number of individualsub-beams involved. Specifically, due to the large number of individualsub-beams contributing to the combined output 1522, the time taken tomeasure and modify the phase of each individual sub-beam with respect tothe other sub-beams so as to dynamically control the phase of thecombined laser output 1522 may be unacceptably long. Furthermore, thesignal to noise ratio may be unacceptably low.

It is a particular feature of a preferred embodiment of the presentinvention that OPA laser 1500 preferably includes a phase modulationsubsystem 1530 for carrying out phase modulation of the combined laseroutput in a scaled manner. More specifically, phase modulation subsystem1530 preferably groups at least a portion of the sub-beams provided bylaser splitting and combining subsystem 1514 into groups and thenperforms phase modulation within each group of sub-beams, only withrespect to other sub-beams within the group. Such group phase modulationis preferably performed in parallel across various individual groups ofsub-beams. Phase modulation subsystem 1530 then preferably optimizes thephase of each group of sub-beams with respect to the phases of otherones of the groups of sub-beams, in order to vary the phase of thecombined laser output 1522, in a manner detailed henceforth.

Phase modulation subsystem 1530 preferably includes a phase controlelectronic module 1532 in operative control of phase modulators 1518.Phase control electronic module 1532 preferably controls each phasemodulator 1518 so as to dynamically modulate the relative phases of thesub-beams along channels 1516, in accordance with the desired far-fieldintensity pattern of output beam 1522, as ascertained by phasemodulation subsystem 1530.

In order to facilitate application of phase variation to output beam1522, a portion of the output of OPA laser 1500 is preferably extractedand directed towards a plurality of detectors 1550. The extractedportion of the output beam preferably functions as a reference beam,based on characteristics of which the required phase variation may becalculated. In the embodiment shown in FIG. 15 , plurality of sub-beamsalong channels 1516 are directed towards a beam splitter 1560. Beamsplitter 1560 preferably splits each sub-beam into a transmitted portion1562 and a reflected portion 1564 in accordance with a predeterminedratio. For example, beam splitter 1560 may split each sub-beam with a99.9% transmitted: 0.01% reflected ratio.

The transmitted portion 1562 of the sub-beams preferably propagatestowards focal lens 1520, at which focal lens 1520 the sub-beams arecombined to form output beam 1522 having a far-field intensity pattern1566. The reflected portion 1564 of the sub-beams preferably propagatestowards a cylindrical lens 1568. Cylindrical lens 1568 is preferablyoperative to receive the reflected portion 1564 of the sub-beams andgroup the sub-beams into a multiplicity of groups, by converging thesub-beams along a direction of curvature of lens 1568. Here, by way ofexample, the sub-beams are shown to be converged into four groups 1570,each group 1570 being made up of four sub-beams.

Preferably, each group 1570 of sub-beams grouped by cylindrical lens1568 forms a beam having a far-field intensity pattern 1572 incident ona surface of corresponding one of plurality of detectors 1550. Eachdetector 1550 preferably samples the group far-field intensity pattern1572 incident thereon. Each detector 1550, in cooperation with acorresponding control electronics sub-module 1574 included in controlmodule 1532, then preferably optimizes the relative phases of thesub-beams within the group of sub-beams 1570 sampled thereby, withrespect to the phases of the other sub-beams within the group 1570. Suchsampling and optimization is preferably carried out in parallel andpreferably simultaneously for ones of far-field intensity patterns 1572across all of detectors 1550. Various algorithms suitable for phaseoptimization include sequential or non-sequential optimizationalgorithms including noise correction algorithms, such as describedabove with reference to FIGS. 1A-4C.

In order to optimize the relative phase of each of groups 1570 withrespect to other ones of groups 1570, a portion of groups 1570 ispreferably directed, by way of an auxiliary beam splitter 1580, to anauxiliary cylindrical lens 1582. It is appreciated that the curvature ofauxiliary cylindrical lens 1582 is preferably orthogonal with respect tothe curvature of cylindrical lens 1568 in order to focus the sub-beams.Auxiliary cylindrical lens 1582 preferably causes groups of sub-beams1570 to converge into a single beam 1584 having a far-field intensitypattern 1586 incident on an auxiliary detector 1588. Auxiliary detector1588 preferably receives thereat a single beam having a far fieldintensity pattern 1586 corresponding to that of a combination of all ofgroups of sub-beams 1570. Auxiliary detector 1588 preferably samples andoptimizes the phases of groups 1570 with respect to each other, incooperation with an additional phase control electronics sub-module 1590included in electronic control module 1532. Particularly preferably, onefunction of phase control electronic module 1532 is to control eachphase modulator 1518 so as to apply a phase shift maximizing the totalpower on auxiliary detector 1588.

It is appreciated that carrying out phase modulation in theabove-described scaled manner, wherein the phase of each sub-beam isoptimized with respect to the phases of other sub-beam members of itsgroup 1570 and the phases of groups 1570 are optimized with respect toeach other so as to vary the phase of the combined laser output 1522, isfar quicker and less complex than optimizing the phase of eachindividual sub-beam with respect to the phases of all of the othersub-beams in OPA 1500. Furthermore, this allows the phase optimizationto be carried out by individual sets of control electronics in eachcontrol electronics sub-module 1574 respectively coupled to eachdetector 1550, rather than requiring a single set of control electronicsand improves the signal to noise ratio.

It is appreciated that the functionality of optimizing the relativephase of each of groups 1570 with respect to other ones of groups 1570may alternatively be carried out by additional group phase modulators,operative to modulate the collective phase of each of groups 1570,rather than by individual phase modulators 1518 operative to modulatethe individual phase of each sub-beam member of each of groups 1570. Anexemplary implementation of such an arrangement is illustrated in FIG.16 and may generally resemble the phase modulation arrangement describedin U.S. Pat. No. 9,893,494, the disclosure of which is herebyincorporated by reference, in some aspects thereof.

As seen in FIG. 16 , system 1500 may be modified by adding a series ofgroup phase modulators corresponding to the number of groups 1570. Here,by way of example, system 1500 comprises 16 sub-beams, four of whichsub-beams are included in each of four groups 1570, such that a total offour additional group phase modulators 1618 may be included in system1500, as seen in FIG. 16 . Each group phase modulator 1618 is preferablycommon to the four channels 1516 forming part of each group 1570 andprovides a phase shift optimizing the collective group phase of thesub-beams along the four channels 1516 connected thereto.

Preferably, ones of group phase modulator 1618 are controlled by anadditional control sub-module 1690, preferably included in controlmodule 1532. Auxiliary detector 1588 is preferably coupled to theadditional control sub-module 1690. It is appreciated that optimizingthe relative phases of groups 1570 with respect to each other by groupphase modulators 1618 rather than by individual sub-beam phasemodulators 1518 may be more efficient and may simplify the phasemodulation process, but requires the employment of additional phasemodulating and circuitry elements, thus increasing the cost andcomplexity of system 1500.

Variation of the phase of combined laser output 1522 preferably providesspatial modulation of the output 1522. It is appreciated that, due tothe scaled nature of the phase modulation carried out by phasemodulation subsystem 1530, the phase of combined laser output 1522 maybe varied very rapidly, at a rate greater than that achievable bymechanical spatial modulation mechanisms. The spatial modulationprovided by OPA laser 1500 may optionally be augmented by additionalmechanical spatial modulation mechanisms, as are known in the art, ormay not involve mechanical spatial modulation.

It is understood that the particular structure and configuration ofoptical elements shown herein, including beam splitter 1560, focal lens1520, cylindrical lens 1568, auxiliary beam splitter 1580 and auxiliarycylindrical lens 1582 is exemplary only and depicted in a highlysimplified form. It is appreciated that OPA laser system 1500 mayinclude a variety of such elements, as well as additional opticalelements, including, by way of example only, additional or alternativelenses, optical fibers and coherent free-space far-field combiners.

Furthermore, it is appreciated that cylindrical lens 1568 may haveoptical properties so as to group the individual sub-beams into mutuallysimilar or identical groups comprising equal numbers of sub-beams.Alternatively, cylindrical lens 1568 may have optical properties so asto group the individual sub-beams into mutually differing groupscomprising different numbers of sub-beams.

An exemplary implementation of an OPA laser system of the typeillustrated in FIG. 15 or FIG. 16 is shown in FIGS. 17A and 17B. Turningnow to FIGS. 17A and 17B, an OPA laser system 1700 is provided whereinan output laser beam from a seed laser (not shown) such as seed laser1512 is split into a plurality of sub-beams along a correspondingplurality of channels 1716. By way of example, the laser output may besplit, by way of example, into a 10×10 matrix of 100 sub-beams along 100corresponding channels 1716. It is appreciated that, for the sake ofclarity of presentation, only selected ones of the sub-beams areillustrated in FIG. 17B. Sub-beams along channels 1716 may subsequentlybe collimated and focused by collimating and focusing elements (notshown) such as collimating and focusing lenses 1519, 1520, to produce acombined output beam.

In order to facilitate application of phase variation to the outputbeam, a portion of the output of OPA laser 1700 is preferably extractedand directed towards a plurality of detectors 1750. The extractedportion of the output beam preferably functions as a reference beam,based on characteristics of which the required phase variation may becalculated. In the embodiment shown in FIGS. 17A and 17B, plurality ofsub-beams along channels 1716 are directed towards a beam splitter 1760.Beam splitter 1760 preferably splits each sub-beam into a transmittedportion 1762 and a reflected portion 1764 in accordance with apredetermined ratio.

The transmitted portion 1762 of the sub-beams is preferably combined toform the output beam. The reflected portion 1764 of the sub-beams ispreferably reflected towards a cylindrical lens 1768, which cylindricallens 1768 is particularly preferred embodiment of cylindrical lens 1568.Cylindrical lens 1768 is preferably operative to receive the reflectedportion 1764 of the sub-beams and cause the sub-beams to converge into amultiplicity of groups along a direction of curvature of cylindricallens 1768. By way of example, in the case of 100 sub-beams, cylindricallens 1768 may cause the sub-beams to converge into ten groups 1770 often sub-beams.

Preferably, each group 1770 of sub-beams grouped by cylindrical lens1768 forms a beam having a far field intensity pattern incident on asurface of corresponding one of plurality of detectors 1750. By way ofexample plurality of detectors 1750 may include ten detectors 1750, eachsampling a group beam comprising ten individual sub-beams. Each detector1750, in cooperation with a corresponding control electronics module(not shown) such as control module 1532, then preferably optimizes thephases of the sub-beams included in the group 1770 of sub-beams sampledthereby, Such sampling and optimization is preferably carried out inparallel and preferably simultaneously across all of detectors 1750.

In order to optimize the relative phase of each of groups 1770 withrespect to the phases of other ones of groups 1770, a portion of groups1770 is preferably directed, by way of an auxiliary beam splitter 1780,to an auxiliary cylindrical lens 1782. It is appreciated that auxiliarycylindrical lens 1782 is a particularly preferred embodiment ofauxiliary cylindrical lens 1582. It is appreciated that the curvature ofauxiliary cylindrical lens 1782 is preferably orthogonal with respect tothe curvature of cylindrical lens 1768 in order to focus the sub-beams.Auxiliary cylindrical lens 1782 preferably focuses groups of sub-beams1770 into one combined beam 1784 incident on an auxiliary detector 1788.

Auxiliary detector 1788 preferably receives thereat a far fieldintensity pattern corresponding to that of a combination of all ofgroups of sub-beams 1770 and samples and optimizes the phases of groups1770 with respect to each other, in cooperation with phase controlelectronics (not shown). It is appreciated that the optimization of thephases of groups 1770 with respect to each other may be by way of phasemodulation of the phases of the individual sub-beams by phase modulators1518, as described hereinabove with reference to FIG. 15 , or may be byway of phase modulation of the phases of the groups of sub-beams bygroup phase modulators 1618, as described hereinabove with reference toFIG. 16 .

Reference is now made to FIG. 18 , which is a simplified schematic planview illustration of an optical phased array laser system includingscaled phase modification of dynamic beams, constructed and operative inaccordance with another preferred embodiment of the present invention.

As seen in FIG. 18 , there is provided an optical phased array (OPA)laser system 1800, which OPA laser 1800 may be of a type generallydescribed hereinabove with reference to FIGS. 1A-4C. OPA laser 800preferably comprises a seed laser 1812 and a laser beam splitting andcombining subsystem 1814. Splitting and combining subsystem 1814preferably receives an output laser beam from seed laser 1812 and splitsthe output laser beam into a plurality of sub-beams along acorresponding plurality of channels 1816. Here, by way of example only,an output from seed laser 1812 may be split into a 4×4 matrix of 16sub-beams along 16 corresponding channels 1816, four of which sub-beamsand channels 1816 are seen in the top view of OPA laser 1800 in FIG. 18. It is appreciated, however, that splitting and combining subsystem1814 may include a fewer or greater number of channels along which theoutput of seed laser 1812 is split, and typically may include a fargreater number of channels such as 32 or more channels.

The relative phase of each sub-beam may be individually modulated by aphase modulator 1818, preferably located along each of channels 1816.Each phase modulated sub-beam produced by the splitting and subsequentphase modulation of the output of seed laser 402 preferably propagatestowards a collimating lens 1819. The individually collimated, phasemodulated sub-beams are subsequently combined, for example at a focalplane of a lens 1820, to form an output beam 1822.

Splitting and combining subsystem 1814 may also provide laseramplification of the sub-beams, preferably following the splitting ofthe output beam of seed laser 1812 into sub-beams and prior to thecombining of the sub-beams to form output beam 1822. Here, by way ofexample, splitting and combining subsystem 1814 is shown to include aplurality of optical amplifiers 1824 located along corresponding ones ofchannels 1816 for amplifying each sub-beam. It is appreciated, however,that such amplification is optional and may be omitted, depending on thepower output requirements of OPA laser 1800.

The phase of output beam 1822, and hence the position and shape of thefar-field intensity pattern thereof, is controlled, at least in part, bythe relative phases of the constituent sub-beams combined to form outputbeam 1822. In many applications, such as laser cutting, laser welding,free-space optical communications and laser additive manufacturing, asdescribed hereinabove, it is desirable to dynamically move and shape thefar-field intensity pattern of the output beam. As described hereinabovewith reference to FIGS. 1A-4C, dynamic variation of parameters of theoutput beam may be achieved by dynamically varying the relative phasesof the individual sub-beams along channels 1816 and thereby varying thephase of the combined laser output 1822 so as to dynamically control theposition and shape of the far-field intensity pattern thereof.

In the case of OPA laser 1800 including a large number of individualsub-beams, phase measurement and corresponding phase modification ofeach sub-beam with respect to the phases of all of the other ones of thesub-beams, may be challenging due to the large number of individualsub-beams involved. Specifically, due to the large number of individualsub-beams contributing to the combined output 1822, the time taken tomeasure and modify the phase of each individual sub-beam with respect tothe other sub-beams so as to dynamically control the phase of thecombined laser output 1822 may be unacceptably long. Furthermore, thesignal to noise ratio may be unacceptably low.

It is a particular feature of a preferred embodiment of the presentinvention that OPA laser 1800 preferably includes a phase modulationsubsystem 1830 for carrying out phase modulation of the combined laseroutput in a scaled manner. More specifically, phase modulation subsystem1830 preferably groups at least a portion of the sub-beams provided bylaser splitting and combining subsystem into groups and then performsphase modulation within each group of sub-beams, only with respect tothe phases of other sub-beams within the group. Such group phasemodulation is preferably performed in parallel across various individualgroups. Phase modulation subsystem 1830 then preferably optimizes thephase of each group of sub-beams with respect to the phases of otherones of the groups of sub-beams, in order to vary the phase of thecombined laser output 1822, in a manner detailed henceforth.

Phase modulation subsystem 1830 preferably includes a phase controlelectronic module 1832 in operative control of phase modulators 1818.Phase control electronic module 1832 preferably controls each phasemodulator 1818 so as to dynamically modulate the relative phases of thesub-beams along channels 1816, in accordance with the desired far-fieldintensity pattern of output beam 1822 and as ascertained by phasemodulation subsystem 1830.

In order to facilitate application of phase variation to output beam1822, a portion of the output of OPA laser 1800 is preferably extractedand directed towards a plurality of detectors 1850. The extractedportion of the output beam preferably functions as a reference beam,based on characteristics of which the required phase variation may becalculated. In the embodiment shown in FIG. 18 , plurality of sub-beamsalong channels 1816 are directed towards a beam splitter 1860. Beamsplitter 1860 preferably splits each sub-beam into a transmitted portion1862 and a reflected portion 1864 in accordance with a predeterminedratio. For example, beam splitter 1860 may split each sub-beam with a99.9% transmitted: 0.01% reflected ratio.

The transmitted portion 1862 of the sub-beams preferably propagatestowards focal lens 1820, at which focal lens 1820 the sub-beams arecombined to form output beam 1822 having a far-field intensity pattern1866. The reflected portion 1864 of the sub-beams is preferablyreflected towards an array of mirrors 1868, each mirror 1868 beingpositioned in spaced relation to a corresponding focusing lens 1869. Byway of example, array of mirrors 1868 may comprise four mirrors 1868positioned in spaced relation to four focusing lenses 1869, two of whichmirrors and focusing lenses are visible in the top view of system 1800in FIG. 18 .

Mirrors 1868 are preferably angled so as to be operative to reflectsub-beams incident thereon towards the corresponding focusing lens 1869and thereby group the reflected portion 1864 of the sub-beams into amultiplicity of groups, here embodied, by way of example, as four groups1870, each group 1870 including four sub-beams, two of which groups areseen in the top view of system 18100 in FIG. 18 .

Preferably, each group of sub-beams reflected at each of mirrors 1868 isfocused by the corresponding focal lens 1869 to form a single beamcomprising group of sub-beams 1870 and having a far-field intensitypattern 1872 incident on a surface of a corresponding one of pluralityof detectors 1850. Each detector 1850, in cooperation with acorresponding control electronics sub-module 1874 included in controlmodule 1832, then preferably optimizes the relative phases of thesub-beams within the group of sub-beams 1870 sampled thereby, withrespect to the phases of the other sub-beams within the group 1870. Suchsampling and optimization is preferably carried out in parallel andpreferably simultaneously for ones of far-field intensity patterns 1872across all of detectors 1850. Various algorithms suitable for phaseoptimization include sequential or non-sequential optimizationalgorithms including noise correction algorithms, as describedhereinabove with reference to FIGS. 1A-4C.

In order to optimize the relative phase of each of groups 1870 withrespect to other ones of groups 1870, a portion of reflected portion1864 is preferably directed, by way of an auxiliary beam splitter 1880,to an auxiliary lens 1882. Auxiliary lens 1882 preferably causes thesub-beams incident thereon to converge into a single beam 1884 having afar-field intensity pattern 1886 incident on an auxiliary detector 1888.Auxiliary detector 1888 preferably receives thereat a single beam havinga far field intensity pattern 1886 corresponding to that of acombination of all of groups of sub-beams 1870. Auxiliary detector 1888preferably samples and optimizes the phases of groups 1870 with respectto each other, in cooperation with a phase control electronicssub-module 1890 included in electronic control module 1832. Particularlypreferably, one function of phase control electronic module 1832 is tocontrol each phase modulator 1818 so as to apply a phase shiftmaximizing the total power on auxiliary detector 1888.

It is appreciated that carrying out phase modulation in theabove-described scaled manner, wherein the phase of each sub-beam isoptimized with respect to the phases of other sub-beam members of itsgroup 1870 and the phases of groups 1870 are optimized with respect toeach other to vary the phase of the combined laser output 1822, is farquicker and less complex than optimizing the phase of each individualsub-beam with respect to the phases of all of the other sub-beams in OP1800. Furthermore, this allows the phase optimization to be carried outby individual sets of control electronics in each control electronicssub-module 1874 coupled to each detector 1850, rather than requiring asingle set of control electronics and improves the signal to noiseratio.

It is appreciated that the functionality of optimizing the relativephase of each of groups 1870 with respect to other ones of groups 1870may alternatively be carried out by additional group phase modulators,operative to modulate the collective phase of each of groups 1870,rather than by individual phase modulators 1818 operative to modulatethe individual phase of each sub-beam member of each of groups 1870. Anexemplary implementation of such an arrangement is illustrated in FIG.19 and may generally resemble the phase modulation arrangement describedin U.S. Pat. No. 9,893,494 in some aspects thereof.

As seen in FIG. 19 , system 1800 may be modified by adding a series ofgroup phase modulators corresponding to the number of groups 1870. Here,by way of example, system 1800 comprises 16 sub-beams, four of whichsub-beams are included in each of four groups 1870, such that a total offour additional group phase modulators 1918 may be included in system1800, as seen in FIG. 19 . Each group phase modulator 1918 is preferablycommon to the four channels 1816 forming part of each group 1870 andprovides a phase shift optimizing the collective group phase of thesub-beams along the four channels 1816.

Preferably, ones of group phase modulator 1918 are controlled by anadditional control sub-module 1990, preferably included in controlmodule 1832. Auxiliary detector 1888 is preferably coupled to theadditional control sub-module 1990. It is appreciated that optimizingthe relative phases of groups 1870 with respect to each other by groupphase modulators 1918 rather than by individual sub-beam phasemodulators 1818 may be more efficient and may simplify the phasemodulation process, but requires the employment of additional phasemodulating and circuitry elements, thus increasing the cost andcomplexity of system 1800.

Variation of the phase of combined laser output 1822 preferably providesspatial modulation of the output 1822. It is appreciated that, due tothe scaled nature of the phase modulation carried out by phasemodulation subsystem 1830, the phase of combined laser output 1822 maybe varied very rapidly, at a rate greater than that achievable bymechanical spatial modulation mechanisms. The spatial modulationprovided by OPA laser 1800 may optionally be augmented by additionalmechanical spatial modulation mechanisms, as are known in the art, ormay not involve mechanical spatial modulation.

It is understood that the particular structure and configuration ofoptical elements shown herein, including beam splitter 1860, focal lens1820, array of mirrors 1868 and corresponding focal lenses 1869 isexemplary only and depicted in a highly simplified form. It isappreciated that OPA laser system 1800 may include a variety of suchelements, as well as additional optical elements, including, by way ofexample only, additional or alternative lenses, optical fibers andcoherent free-space far-field combiners.

Furthermore, it is appreciated that mirrors 1868 and corresponding focallenses 1869 may have mutually similar or identical optical properties,so as to group the individual sub-beams into mutually similar oridentical groups comprising equal numbers of sub-beams. Alternatively,mirrors 1868 and corresponding focal lenses 1869 may have mutuallydifferent optical properties so as to group the individual sub-beamsinto mutually differing groups comprising different numbers ofsub-beams.

An exemplary implementation of an OPA laser system of the typeillustrated in FIG. 18 or FIG. 19 is shown in FIGS. 20A and 20B. Turningnow to FIGS. 20A and 20B, an OPA laser system 2000 is provided whereinan output laser beam from a seed laser (not shown) such as seed laser1812 is split into a plurality of sub-beams along a correspondingplurality of channels 2016. Here, by way of example only, the laseroutput may be split into a 10×10 matrix of 100 sub-beams along 100corresponding channels 2016, only selected ones of which sub-beams areillustrated in FIG. 20B for the sake of clarity of presentation.Sub-beams along channels 2016 may subsequently be collimated and focusedby collimating and focusing elements (not shown) such as collimating andfocusing lenses 1819, 1820, to produce a combined output beam.

In order to facilitate application of phase variation to the outputbeam, a portion of the output of OPA laser 2000 is preferably extractedand directed towards a plurality of detectors 2050. The extractedportion of the output beam preferably functions as a reference beam,based on characteristics of which the required phase variation may becalculated. In the embodiment shown in FIGS. 20A and 20B, plurality ofsub-beams along channels 2016 are directed towards a beam splitter 2060.Beam splitter 2060 preferably splits each sub-beam into a transmittedportion 2062 and a reflected portion 2064 in accordance with apredetermined ratio.

The transmitted portion 2062 of the sub-beams is preferably combined toform the output beam. The reflected portion 2064 of the sub-beams ispreferably reflected towards an array of mirrors 2068, each mirror 2068being positioned in spaced relation to a corresponding focusing lens2069. It is appreciated that array of mirrors 2068 and lenses 2069 areparticularly preferred embodiments of array of mirrors 1868 and focusinglenses 1869.

Mirrors 2068 are preferably angled so as to be operative to reflectsub-beams incident thereon towards the corresponding focusing lens 2069and thereby group the reflected portion 2064 of sub-beams into amultiplicity of groups, here embodied, by way of example, as fourgroups, each group 2070 including 25 sub-beams. Preferably, each set ofsub-beams reflected at each of mirrors 2068 is focused by thecorresponding focal lens 2069 to form a single beam including group of25 sub-beams 2070. Each group of sub-beams 2070 is incident on a surfaceof corresponding one of plurality of detectors 2050. Each detector 2050preferably samples the far-field intensity pattern incident thereon.Each detector 2050, in cooperation with a corresponding controlelectronics sub-module (not shown) such as control electronicssub-module 1874 included in control module 1832, then preferablyoptimizes the phases of the sub-beams included in the group of sub-beams2070 sampled thereby, in order for the combined phases to produce adesired group far-field intensity pattern. Such sampling andoptimization is preferably carried out in parallel and preferablysimultaneously for ones of far-field intensity patterns across all ofdetectors 2050.

In order to optimize the relative phase of each of groups 2070 withrespect to other ones of groups 2070, a portion of the reflected portion2064 is preferably directed, by way of an auxiliary beam splitter 2080,to an auxiliary lens 2082. Auxiliary lens 2082 preferably causes aportion of the reflected portion 2064 to converge into a single beam2084 incident on an auxiliary detector 2088. Auxiliary detector 2088preferably receives thereat a single beam having a far field intensitypattern corresponding to that of a combination of all of the sub-beams.Auxiliary detector 2088 preferably samples and optimizes the phases ofgroups 2070 with respect to each other, in cooperation with phasecontrol electronics included in electronic control module 1832.

It is appreciated that the optimization of the phases of groups 2070with respect to each other may be by way of phase modulation of thephases of the individual sub-beams by phase modulators 1818, asdescribed hereinabove with reference to FIG. 18 , or may be by way ofphase modulation of the phases of the groups of sub-beams by group phasemodulators 1918, as described hereinabove with reference to FIG. 19 .

It is understood that in the above-described embodiments of OPA lasers1500, 1700, 1800 and 2000 of FIGS. 15-20B, phase modulation ispreferably carried out in a scaled manner, with multiple detectors suchas detectors 1550, 1750, 1850 and 2050 employed for simultaneouslyperforming phase measurements of sub-beams within multiple groups and asingle detector, such auxiliary detector 1586, 1786, 1886 and 2086,employed for performing phase measurements of a single beam includingthe multiple groups.

It is appreciated, however, that a system constructed and operative inaccordance with preferred embodiments of the present invention may befurther scalable, to include still additional hierarchies of detectorsand corresponding optical elements, depending on the number of sub-beamsinvolved.

By way of example, as shown in FIG. 21 , OPA laser system 1500 may bemodified to include additional focusing lenses 2102 for focusing groups1570 of sub-beams into intermediate groups 2104 which intermediategroups are incident on intermediate detectors 2106. Intermediate groups2104 are then further combined and incident on a single detector 2108,at which single detector 2108 intermediate groups 2104 are preferablyphase modified with respect to each other.

It is additionally understood that any of the OPA laser systemsdescribed hereinabove with reference to FIGS. 15-21 may be modified byreplacing one or more of the individual detectors therein with multipledetectors and corresponding multiple closely spaced optical pathways, inorder to improve the sampling of the output beams, in accordance withembodiments of the present invention described hereinabove withreference to FIGS. 6-8 . Furthermore, any of the OPA laser systemsdescribed hereinabove with reference to FIGS. 15-21 may alternatively bemodified to include a transmissive or reflective detector mask maskingone or more of the multiple detectors employed therein, in accordancewith embodiments of the present invention described hereinabove withreference to FIGS. 9-12 , in order to further improve the sampling ofthe output beams.

It is furthermore understood that any of the OPA laser systems describedhereinabove with reference to FIGS. 15-21 may be modified to includevoltage-phase calibration functionality, in accordance with preferredembodiments of the present invention described hereinabove withreference to FIGS. 13 and 14 , in order to ensure correct calibration ofthe phase modulators employed therein.

Reference is now made to FIGS. 22A and 22B, which are simplifiedschematic illustrations of respective first and second focal states ofan optical phased array laser system constructed and operative inaccordance with a preferred embodiment of the present invention.

As seen in FIGS. 22A and 22B, there is provided a laser system 2200preferably including an optical phased array (OPA) laser 2202. OPA lasersystem 2200 may be of the type generally described in U.S. Pat. No.9,584,224 or in U.S. patent application Ser. No. 15/406,032, assigned tothe same assignee as the present invention, the contents of which areincorporated herein by reference. Alternatively, OPA laser system 2200may be a laser system of the type described in reference to any one, ora combination of ones, of FIGS. 1A-21 hereinabove.

As best seen at an enlargement 2210, OPA laser 2202 preferably includesa seed laser 2212 and a laser beam splitting and combining subsystem2214 receiving a laser output from seed laser 2212 and providing acombined laser output. Laser beam splitting and combining subsystem 2214preferably includes a plurality of phase modulators 2218 for varying aphase of the combined laser output, preferably following the splittingof the laser output from seed laser 2212 and prior to the combiningperformed by splitting and combining subsystem 2214.

Each phase modulated sub-beam produced by the splitting and subsequentphase modulation of the output of seed laser 2212 preferably propagatestowards a collimating lens 2219. The individually collimated, phasemodulated sub-beams are subsequently combined, for example at a focallens 2220, to form an output beam 2222.

Splitting and combining subsystem 2214 may also provide laseramplification of the sub-beams, preferably following the splitting ofthe output beam of seed laser 2212 into sub-beams and prior to thecombining of the sub-beams to form output beam 2222. Here, by way ofexample, splitting and combining subsystem 2214 is shown to include aplurality of optical amplifiers 2224 for amplifying each sub-beam. It isappreciated, however, that such amplification is optional and may beomitted, depending on the power output specifications of OPA laser 2200.

The phase of output beam 2222, and hence the position and shape of thefar-field intensity pattern thereof, is controlled, at least in part, bythe relative phases of the constituent sub-beams combined to form outputbeam 2222. As described hereinabove with reference to FIGS. 1A-5G, inmany applications, such as laser cutting, laser welding, laser additivemanufacturing and optical free space communications, it is desirable todynamically move and shape the far-field intensity pattern of the outputbeam 2222. This may be achieved in laser system 2200 by laser splittingand combining subsystem 2214 dynamically varying the relative phases ofthe individual sub-beams and thereby varying the phase of the combinedlaser output 2222 so as dynamically to control the position and shape ofthe far-field intensity pattern thereof.

The relative phases of the sub-beams are preferably predetermined inaccordance with the desired laser output pattern. Particularlypreferably, the varying relative phases are applied by a phase controlsubsystem 2230. Phase control subsystem 2230 preferably forms a part ofa control electronics module 2232 in OPA laser system 2200 andpreferably controls each phase modulator 2218 so as to dynamicallymodulate the relative phases of the sub-beams, preferably as describedhereinabove with reference to phase control subsystem 130, 230, 330, 430of FIGS. 1A, 2A, 3A and 4A respectively.

Due to noise inherent in OPA system 2200, output beam 2222 may havenoise. Noise in output beam 2222 is typically phase noise created bythermal or mechanical effects and/or by the amplification process in thecase that optical amplifiers 2224 are present in OPA system 2200. In thecase that output beam 2222 has noise, OPA system 2200 may include anoise cancellation subsystem 2240 operative to provide a noisecancellation phase correction output in order to cancel out the noise inoutput beam 2222 in a manner detailed henceforth.

Particularly preferably, noise cancellation subsystem 2240 employs analgorithm to sense and correct phase noise in the combined laser output,preferably, although not necessarily, of the type described hereinabovewith reference to FIGS. 1A-4C. The noise cancellation phase correctionoutput is preferably provided by noise cancellation subsystem 2240 tophase modulators 2218 so as to correct phase noise in output beam 2222and thus avoid distortion of the shape and position of the far fieldintensity pattern of output beam 2222 that would otherwise be caused bythe noise. Noise cancellation subsystem 2240 may be included in controlelectronics module 2232.

Alternatively, in the case that noise in output beam 2222 is not ofsignificance, noise cancellation subsystem 2240 may be obviated from OPAsystem 2200 and noise correction correspondingly not performed.

In order to facilitate application of phase variation and noisecorrection if relevant to output beam 2222, a portion of the output ofOPA laser 2202 is preferably extracted and directed towards at least onedetector 2250. Here, by way of example, at least one detector 2250 isshown to be embodied as a single detector 2250. However, it isunderstood that at least one detector 2250 may be embodied as multipledetectors receiving a portion of the output of OPA laser 2202 by way ofclosely spaced optical pathways, as described hereinabove with referenceto FIGS. 6-8 , or may be embodied as at least one detector receiving aportion of the output of OPA laser 2202 via a transmissive or reflectiveoptical mask, as described hereinabove with reference to FIGS. 9-12 .The extracted portion of the output beam preferably functions as areference beam, based on characteristics of which the required noisecorrection and/or phase variation may be calculated.

In accordance with a preferred embodiment of the present invention,plurality of sub-beams along channels 2216 are directed towards a beamsplitter 2260. Beam splitter 2260 preferably splits each sub-beam into atransmitted portion 2262 and a reflected portion 2264 in accordance witha predetermined ratio. For example, beam splitter 2260 may split eachsub-beam with a 99.9% transmitted: 0.01% reflected ratio.

The transmitted portion 2262 of the sub-beams preferably propagatestowards focal lens 2220, at which focal lens 2220 the sub-beams arecombined to form output beam 2222 having a far-field intensity pattern2266. The reflected portion 2264 of the sub-beams is preferablyreflected towards an additional focal lens 2268, at which additionalfocal lens 2268 the sub-beams are combined to form an output referencebeam 2270 having a far-field intensity pattern 2272 incident on asurface of one or more of plurality of detectors 2250.

In certain applications, output beam 2222 is preferably directed towardsa substrate 2280 upon which substrate 2280 far-field intensity pattern2266 is preferably incident. Substrate 2280 may be a workpiece beingprocessed by OPA laser 2202. For example, OPA laser 2202 may beoperative to additively manufacture, cut, weld, sinter or otherwiseprocess workpiece 2280. Phase control subsystem 2230 preferably varies aphase of the output beam 2222 in order to focus the output beam 2222 onsubstrate 2280. It is appreciated that in the absence of the applicationof such phase variation by phase control subsystem 2230, output beam2222 would not be focused on the substrate 2280.

It is a particular feature of a preferred embodiment of the presentinvention that focal lens 2220 is preferably designed such that theoutput beam 2222 of OPA laser 2202 in the absence of the application ofphase variation thereto, would not be focused by lens 2220 on thesurface of substrate 2280. By way of example, as appreciated fromconsideration of FIG. 22A illustrating the configuration of output beam2222 in the absence of the application of phase variation thereto, focallens 2220 may be optically designed to focus non-phase varied collimatedwavefronts 2282 comprising output beam 2222 at a focal point 2284 abovea surface of the substrate 2280.

As appreciated from consideration of FIG. 22B, illustrating theconfiguration of output beam 2222 in the case of the application ofphase variation thereto, phase-variation of the output beam 2222preferably serves to modify a shape and hence focus of wavefronts 2282,as seen in the case of representative phase-modified wavefronts 2286,which phase-modified wavefronts 2286 are preferably focused on substrate2280 by way of focal lens 2220. It is appreciated that the focusing ofoutput beam 2222 on substrate 2280 is thus achieved by phase variationthereof in combination with focal lens 2220, as illustrated in FIG. 22B,rather than solely by focal lens 2220.

As a result of focusing of output beam 2222 on the substrate 2280 beingachieved by phase variation thereof, back-scatter arising from substrate2280 is correspondingly not focused by focal lens 2220 on OPA laser2202. As is well known in the art, back-scatter from surfaces treated bylaser beams typically returns to the laser and may cause damage thereto,particularly in laser amplification systems. Such damage is avoided inthe present invention, due to focal lens 2220 not focusing back-scattertowards OPA laser 2202 and back-scatter therefore not reaching anddamaging OPA laser 2202.

An exemplary return path of back-scatter from substrate 2280 towards OPAlaser 2202 is illustrated in FIG. 23 . As seen in FIG. 23 ,back-scattered laser beams 2300 emanating from substrate 2280 preferablyarrive at focal lens 2220. However, back-scattered laser beams 2300 arepreferably not focused on OPA laser 2202 by focal lens 2220, therebypreventing damage thereto. It is understood that should focal lens 2220be designed to focus non-phase modified laser output from OPA laser 2202on substrate 2280, as is typically the case in conventional lasersystems, the path of back-scattered beams 2300 would be correspondinglyfocused by focal lens 2220 on OPA laser 2202, thus possibly causingdamage thereto.

It is appreciated that, in certain embodiments of the present invention,the focusing of the output of OPA laser 2202 on substrate 2280 may beperformed solely by way of appropriate phase variation of the outputbeam 2222, such that focal lens 2220 may be obviated.

As described hereinabove with reference to FIGS. 1A-23 , an output froma seed laser may be directed to an amplification system for theamplification thereof. As is well known by those skilled in the art,defects in the laser output by a seed laser feeding an amplificationsystem may result in damage to the amplification system. Typical defectsin the laser output by the seed laser responsible for causing damage toan amplification system connected thereto may include reduction of powerof the seed laser output and degradation of the laser line width.Resultant damage to the amplification system may occur extremelyrapidly, on the order of several nanoseconds, and before the responsetime of internal sensing mechanisms that may be included in theamplification system.

Preferred embodiments of the present invention for preventing damage toan amplification system in the event of failure of a seed laserconnected thereto are now described with reference to FIGS. 24-33 . Itis understood that the seed laser failure protection systems describedhereinbelow may be incorporated in an OPA laser of any of the typesdescribed hereinabove with reference to FIGS. 1A-23 or may beincorporated in any other laser system including a seed laser andamplifier connected thereto.

Turning now to FIG. 24 , as seen in FIG. 24 there is provided a lasersystem 2400 preferably including a seed laser 2402 providing a laseroutput and an amplifying subsystem, here embodied by way of example as apower amplifier 2404, receiving the laser output from seed laser 2402and amplifying the laser output to provide an amplified laser output2406. Laser system 2400 may be embodied, by way of example, a MasterOscillator Power Amplifier (MOPA) laser or may be any other laser systemincluding a seed laser and power amplifier. The laser output from seedlaser 2402 preferably reaches power amplifier 2404 via a first opticalpath 2408, here embodied, by way of example, as comprising a coiledoptical fiber 2410.

In order to detect possible defects in the laser output of seed laser2402, system 2400 further preferably includes a detector subsystem,preferably embodied as seed sensor 2420, receiving the output from seedlaser 2402. The laser output from seed laser 2402 preferably reachesdetector subsystem 2420 via a second optical path 2422. Detectorsubsystem 2420 may include one or more sensors for sensing properties ofthe laser output and, more specifically, for detecting possible faultsin the laser output. Sensor subsystem 2420 is preferably operativelycoupled to power amplifier 2404. Sensor subsystem 2420 is preferablyconfigured to deactivate power amplifier 2404 upon detection of faultsin the laser output from seed laser 2402.

It is a particular feature of a preferred embodiment of the presentinvention that a first time of flight (TOF=T1) of the laser output alongthe first optical path 2408 from seed laser 2402 to power amplifier 2404is greater than a combination of a second time of flight (TOF=T2) of thelaser output along the second optical path 2422 from seed laser 2402 tosensor subsystem 2420 and a time taken for sensor subsystem 2420 todeactivate power amplifier 2404.

As a result of the time of flight of the laser output from the seedlaser 2402 to the power amplifier 2404 being relatively long, the sensorsubsystem 2420 is preferably capable of detecting faults in the laseroutput received thereat and deactivating the power amplifier 2404 priorto the power amplifier 2404 receiving the faulty laser output, therebypreventing damage to the power amplifier 2404.

Extension of the time of flight of the laser output from the seed laser2402 to the power amplifier 2404, in order to allow time for the sensor2420 to sense faults in the laser output and deactivate the poweramplifier 2404 when necessary prior to receipt of the faulty laseroutput by the power amplifier 2404, is achieved in the embodiment of thepresent invention illustrated in FIG. 24 by inclusion of fiber coil 2410along the first optical path. By way of example, fiber coil 2410 mayhave a physical length of 10 km and a time of flight of the laser outputtherealong may be approximately 50 microseconds. In the case of thedevelopment of faults in the output from seed laser 2402, poweramplifier 2404 will therefore continue to receive a non-faulty inputsignal for the duration of 50 microseconds following the onset of thefaulty output signal from seed laser 2402.

The optical path between the seed laser 2402 and the sensor subsystem2420 does not include coil 2410 and may be a direct and thus far shorteroptical path. The time of flight of the laser output from seed laser2402 to sensor subsystem 2420 is hence preferably much shorter than 50microseconds, for example of the order of 30 microseconds or less.Following the development of faults in the output from seed laser 2402,sensor subsystem 2420 thus may rapidly receive the laser output, detectfaults therein and switch off power amplifier 2404, all prior toexpiration of the time delay between the seed laser 2402 and the poweramplifier 2404. As a result, power amplifier 2404 is preferably switchedoff by sensor subsystem 2420 before power amplifier 2404 receives thefaulty signal detected by sensor subsystem 2420, thereby preventingdamage to power amplifier 2404.

It is appreciated that the extension of the optical path between theseed laser 2402 and power amplifier 2404, and hence the increase in thetime of flight therealong, in comparison to the optical path time andlength between the seed laser 2402 and the sensor subsystem 2420, is notlimited to being achieved by way of inclusion of a fiber coil along theoptical path between the seed laser 2402 and power amplifier 2404.Rather, the optical path between the seed laser 2402 and power amplifier2404 may be extended by any suitable means, including, for example, theinclusion of an optical delay line 2500 therealong, as illustrated inFIG. 25 . Furthermore, the optical path between seed laser 2402 andpower amplifier 2404 may be a free space optical path 2600, asillustrated in FIG. 26 , in which case the time of flight therealong maybe extended by use of optical elements such as reflecting mirrors. It isappreciated, however, that the inclusion of coiled fiber 2410 in firstoptical path 2408 may be particularly advantageous due to the compactconfiguration thereof and due to the maintenance of the optical mode ofthe seed laser output by the coiled fiber 2410.

It is appreciated that the particular configuration of coiled fiber 2410illustrated in FIG. 24 is representative and exemplary only. Coiledfiber 2410 may be embodied in any suitable form and may be adapted forlaser output to travel therealong in a single direction or in aback-and-forth manner so as to further increase the effective length ofthe optical path provided by coiled fiber 2410.

Reference is now made to FIG. 27 , which is a simplified schematicdiagram of a laser amplifying system including a seed laser failureprotection system constructed and operative in accordance with yetanother preferred embodiment of the present invention.

As seen in FIG. 27 , there is provided a laser system 2700 preferablyincluding a seed laser 2702 providing a laser output. Seed laser 2702 ispreferably connected to a first amplifier 2703, which first amplifier2703 is preferably connected in turn to a second amplifier 2704 hereembodied by way of example as a power amplifier 2704, providing anamplified laser output 2706. Laser system 2700 may be embodied, by wayof example, a Master Oscillator Power Amplifier (MOPA) laser or may beany other laser system including a seed laser and power amplifier.

As is well known by those skilled in the art, and as detailedhereinabove, defects in the laser output by seed laser 2702 may resultin damage to power amplifier 2704. Typical defects in the laser outputby seed laser 2702 causing damage to power amplifier 2704 may includecessation or reduction of power of the seed laser output and degradationof the laser line width. Such damage to the power amplifier may occurextremely rapidly, on the order of several nanoseconds, and before theresponse time of internal sensing mechanisms that may be included inpower amplifier 2704.

In order to avoid damage to power amplifier 2704 as a result of defectsin the output of seed laser 2702, it is a particular feature of apreferred embodiment of the present invention that laser system 2700includes additional amplifier 2703. Preferably, additional amplifier2703 provides far lower amplification than that provided by poweramplifier 2704 and is included in system 2700 for the purposes ofpreventing damage to power amplifier 2704 upon degradation of laseroutput from seed laser 2702 rather than for the purposes ofamplification of the laser output from seed laser 2702 per se.

In operation of system 2700, the laser output from seed laser 2702 ispreferably received by first amplifier 2703. First amplifier 2703preferably provides a first amplified laser output, which firstamplified laser output is preferably received and amplified by secondamplifier 2704.

Upon cessation of laser output from seed laser 2702, due to faultyoperation of seed laser 2702, first amplifier 2703 no longer receivesthe laser output from seed laser 2702. In this case, first amplifier2703 generates amplified spontaneous emission, which amplifiedspontaneous emission is received by second amplifier 2704.Alternatively, first amplifier 2703 may be configured such that uponcessation of laser output from seed laser 2702, first amplifier 2703begins operating as a laser and generates an additional laser output.

It is understood that second amplifier 2704 thus continues to receive aninput signal in the form of amplified spontaneous emission or in theform of an additional laser output from first amplifier 2703, even inthe case that seed laser 2702 has ceased to provide a laser output. Theamplified spontaneous emission provided by first amplifier 2703 tosecond amplifier 2704 is sufficient to prevent damage to secondamplifier 2704, which damage would otherwise be likely to occur due tocessation of the provision of a signal thereto. It is understood thatsystem 2700 may additionally include a sensor connected to seed laser2702 to sense faults in the laser output from seed laser 2702 anddeactivate the second amplifier 2704 accordingly.

It is appreciated that during proper operation of seed laser 2702, thefirst amplification provided by first amplifier 2703 is preferablynegligible in comparison to the second, primary amplification providedsecond amplifier 2704.

As seen in FIG. 27 , laser output from seed laser 2702 may be feddirectly to first amplifier 2703. Alternatively, as illustrated in FIG.28 , additional elements may be inserted interfacing seed laser 2702 andfirst amplifier 2703. Particularly, a filter may be inserted betweenseed laser 2702 and first amplifier 2703 in order to filter out laserbeams of unacceptably narrow line width and thus prevent such laserbeams from reaching and damaging second amplifier 2704.

A particularly preferred embodiment of a line width filter 2800 suitablefor use in the present invention is illustrated in FIG. 28 .

Turning now to FIG. 28 , filter structure 2800 is seen to be implementeddownstream of seed laser 2702 and upstream of first amplifier 2703. Thelaser output from seed laser 2702 is preferably split into two parts ata splitter 2805 on entry to filter 2800 and recombined at a recombiner2806 prior to exit from filter 2800. A first part of the split laseroutput from seed laser 2702 preferably travels along a first arm 2807 offilter 2800 between splitter 2805 and recombiner 2806. A second part ofthe split laser output from seed laser 2702 preferably travels along asecond arm 2808 of filter 2800 between splitter 2805 and recombiner2806. As appreciated from a comparison of first and second arms 2807 and2808, first arm 2807 preferably includes an additional portion 2809 incomparison to second arm 2808 and thus is longer than second arm 2808.

In the case that the laser output from seed laser 2702 is ofunacceptably narrow line width, the laser outputs from first and secondarms 2807 and 2808, when recombined at recombiner 2806, will mutuallyinterfere due to the relatively high coherence thereof. The recombinedbeam is preferably detected by a detector 2810, which detector 2810 ispreferably connected to an electronic control module 2811. Electroniccontrol module 2811 is preferably a coherent beam combining (CBC) card,in operative control of a phase modulator 2812 located along second arm2808. Phase modulator 2812 is preferably operated by electronic controlcard 2811 to alter a phase of the beam along second arm 2808, such thatsubstantially all of the recombined beam at recombiner 2806 is directedtowards detector 2810. The recombined beam thus does not proceed towardsfirst amplifier 2703 and hence does not reach and cause damage to secondamplifier 2704. The receipt of a laser output from seed laser 2702 byfirst amplifier 2703 is thereby halted and first amplifier 2703generates one of amplified spontaneous emission or additional laseroutput, as detailed hereinabove.

In the case that seed laser 2702 is operating properly and the laseroutput from seed laser 2702 is of acceptably wide line width, the laseroutputs from first and second arms 2807 and 2808, when recombined atrecombiner 2806, will not mutually interfere. This is because the linewidth is sufficiently wide such that the coherence is relatively low andtherefore little or no mutual interference occurs. In this case, a partof the laser output at recombiner 2806 will continue towards firstamplifier 2703 and a part of the laser output at recombiner 2806 will bedelivered to detector 2810. The laser output received by first amplifier2703 is preferably subsequently provided by first amplifier 2703 tosecond amplifier 2704, as outlined above with reference to system 2700.

It is understood that the damage protection system illustrated in FIGS.27 and 28 , including additional amplifier 2703 and filter structure2800, may be employed alone or in combination with any one of theprotection systems illustrated in FIGS. 24-26 .

Reference is now made to FIG. 29 , which is a simplified schematicdiagram of a laser amplifying system including a seed laser failureprotection system constructed and operative in accordance with yet afurther preferred embodiment of the present invention.

As seen in FIG. 29 , there is provided a laser system 2900 preferablyincluding a seed laser 2902 providing a first laser output 2903 and anamplifying subsystem, here embodied by way of example as a poweramplifier 2904, receiving the first laser output 2903 from seed laser2902 and amplifying the laser output to provide an amplified laseroutput 2906. Laser system 2900 may be embodied, by way of example, aMaster Oscillator Power Amplifier (MOPA) laser or may be any other lasersystem including a seed laser and power amplifier.

In order to detect possible defects in the laser output of seed laser2902, system 2900 further preferably includes a detector subsystem,preferably embodied as a seed sensor 2920, receiving the output fromseed laser 2902. Sensor subsystem 2920 may include one or more sensorsfor sensing properties of the laser output and, more specifically, fordetecting possible faults in the laser output. Sensor subsystem 2920 ispreferably operatively coupled to power amplifier 2904. Sensor subsystem2920 is preferably configured to deactivate power amplifier 2904 upondetection of faults in the laser output from seed laser 2902.

It is a particular feature of a preferred embodiment of the presentinvention that laser system 2900 preferably includes an auxiliary lasersubsystem, here preferably embodied as an auxiliary seed laser 2930.Auxiliary seed laser 2930 preferably provides a second laser output 2932to amplifier 2904, which second laser output 2932 is preferably of asignificantly lower power than a power of first laser output 2903. Byway of example only, first laser output 2903 may have a first power inthe range of 80-100 milliwatts whereas second laser output 2932 may havea second power in the range of 50-70 milliwatts.

Auxiliary seed laser 2930 preferably provides second laser output 2932at least upon cessation of seed laser 2902 providing first laser output2903 to amplifier 2904. Particularly preferably, auxiliary seed laser2930 preferably operates continuously so as to provide second laseroutput 2932 to amplifier 2904 both concurrently with seed laser 2902providing first laser output 2903 thereto as well as upon cessation ofseed laser 2902 providing first laser output 2903.

During proper operation of seed laser 2902, amplifier 2904 preferablyreceives both first laser output 2903 from seed laser 2902 and secondlaser output 2932 from auxiliary seed laser 2930. Due to the power ofsecond laser output 2932 being significantly lower than the power offirst laser output 2903, the contribution of second laser output 2903 toamplified laser output 2906 is preferably negligible. Preferably,although not necessarily, second laser output 2932 is of a differentwavelength than first laser output 2903, in order for further reduce theinfluence of second laser output 2932 on amplified laser output 2906. Byway of example only, first laser output 2903 may have a first wavelengthin the range of 1060-1070 nm whereas second laser output 2932 may have asecond wavelength in the range of 1070-1080 nm.

Upon cessation of laser output from seed laser 2902, due to faultyoperation of seed laser 2902 as sensed by sensor subsystem 2920, sensorsubsystem 2920 is preferably operative to deactivate amplifier 2904. Dueto the finite response time of amplifier 2904 and detector subsystem2920, amplifier 2904 is not instantaneously deactivated but rathercontinues to operate for a finite period of time following cessation oflaser output from seed laser 2902. It is understood that during thistime, amplifier 2904 no longer receives first laser output 2903 fromseed laser 2902. However, auxiliary seed laser 2930 preferably continuesto provide second laser output 2932 to amplifier 2904. It is understoodthat amplifier 2904 thus continues to receive an input signal in theform of second laser output 2932, even in the case that seed laser 2902has ceased to provide a laser output. The second laser output 2932provided by auxiliary seed laser 2930 to amplifier 2904 is sufficient toprevent damage to amplifier 2904, which damage would otherwise be likelyto occur due to cessation of the provision of a signal thereto, prior toamplifier 2904 being deactivated by sensor 2920.

Reference is now made to FIG. 30 , which is a simplified schematicdiagram of a laser amplifying system including a seed laser failureprotection system constructed and operative in accordance with a stillfurther preferred embodiment of the present invention.

As seen in FIG. 30 , there is provided a laser system 3000 preferablyincluding a seed laser 3002 providing a first laser output 3003 and anamplifying subsystem, here embodied by way of example as a poweramplifier 3004, receiving the first laser output 3003 from seed laser3002 and amplifying the laser output to provide an amplified laseroutput 3006. Laser system 3000 may be embodied, by way of example, aMaster Oscillator Power Amplifier (MOPA) laser or may be any other lasersystem including a seed laser and power amplifier.

In order to detect possible defects in the laser output of seed laser3002, system 3000 further preferably includes a detector subsystem 3020receiving the output from seed laser 3002. Detector subsystem 3020 mayinclude one or more sensors for sensing properties of the laser outputand, more specifically, for detecting possible faults in the laseroutput. Sensor subsystem 3020 is preferably operatively coupled to poweramplifier 3004. Sensor subsystem 3020 is preferably configured todeactivate power amplifier 3004 upon detection of faults in the laseroutput from seed laser 3002.

It is a particular feature of a preferred embodiment of the presentinvention that laser system 3000 preferably includes a pair of gratings3030. Pair of gratings 3030 preferably includes a first reflectiongrating 3032 preferably positioned at an entry 3034 of amplifier 3004and a second reflection grating 3036 preferably positioned at an exit3038 of amplifier 3004. Pair of gratings 3030 in combination withamplifier 3004 preferably form a preferred embodiment of an auxiliarylaser subsystem 3040.

During proper operation of seed laser 3002, amplifier 3004 preferablyreceives first laser output 3003 from seed laser 3002 and amplifiesfirst laser output 3003 to provide amplified laser output 3006.

Upon cessation of laser output from seed laser 3002, due to faultyoperation of seed laser 3002 as sensed by sensor subsystem 3020, sensorsubsystem 3020 is preferably operative to deactivate amplifier 3004. Dueto the finite response time of amplifier 3004 and sensor subsystem 3020,amplifier 3004 is not instantaneously deactivated but rather typicallycontinues to operate for a finite period of time following cessation oflaser output from seed laser 3002. It is understood that during thistime, amplifier 3004 no longer receives a laser output from seed laser3002. In this case, reflection gratings 3030 preferably provide a signalfeedback to amplifier 3004, such that amplifier 3004 in combination withpair of gratings 3030 preferably begins to operate as a laser.Reflection gratings 3030 preferably have a relatively low reflectancesuch that the signal feedback provided by reflection gratings 3030 is oflower power than the power of the laser output 3003 of seed laser 3002.

Particularly preferably, although not necessarily, pair of gratings 3030are reflective at a wavelength different than the wavelength of thefirst laser output 3003 of seed laser 3002, such that during properoperation of seed laser 3002 gratings 3030 have negligible influence onamplified output 3006. By way of example only, first laser output 3003may have a wavelength in the range of 1060-1070 nm whereas gratings 3030may be reflective at a wavelength in the range of 1090-1100 nm.

It is understood that amplifier 3004 thus continues to receive an inputsignal in the form of signal feedback from gratings 3030, even in thecase that seed laser 3002 has ceased to provide a laser output. As aresult, amplifier 3004 in combination with gratings 3030 begins tooperate as a laser upon cessation of operation of seed laser 3002,thereby preventing damage to amplifier 3004, which damage wouldotherwise be likely to occur due to cessation of the provision of asignal thereto.

As seen in FIGS. 29 and 30 , laser output from seed lasers 2902, 3002may be fed directly to amplifiers 2904, 3004 respectively.Alternatively, as illustrated in FIGS. 31 and 32 , additional elementsmay be inserted interfacing the seed laser and amplifier. Particularly,a line width filter, such as filter 2800 or any other suitable filter,may be inserted between seed lasers 2902, 3002 and amplifiers 2904, 3004respectively in order to filter out laser beams of unacceptably narrowline width and thus prevent such laser beams from reaching and damagingamplifiers 2904, 3004.

As detailed hereinabove, each of the laser systems described withreference to FIGS. 24-32 may include a detector subsystem, such asdetector subsystem 2420, 2920 and 3020. The detector subsystem ispreferably embodied as at least one sensor for sensing the output fromthe seed laser. A particularly preferred embodiment of a sensor forminga part of a detector subsystem such as detector subsystem 2420, 2920 and3020 is illustrated in FIG. 33 . It is appreciated, however, that thesensor illustrated in FIG. 33 is not limited to use in systems of thetype described herein and may be incorporated as a laser output sensorin any laser system benefitting from the use thereof.

As seen in FIG. 33 , there is provided a detector subsystem 3320. Laseroutput from a seed laser preferably enters sensor subsystem 3320 at aninput point 3330 and travels towards a splitter 3334. At splitter 3334,a small portion such as 1% of the laser output is directed towards adetector 3336 and the remaining portion of the laser output continuestowards a sensor amplifier 3340. Sensor amplifier 3340 is preferably alower power amplifier than power amplifier 2404, 2704, 2904 or 3004.Sensor amplifier 3340 preferably outputs an amplified laser output,which amplified laser output is preferably delivered to an additionaldetector 3342 by way of an elongate optical fiber 3344.

In operation of detector subsystem 3320, in the case that the outputfrom the seed laser ceases, the intensity of the amplified laser outputdetected at additional detector 3342 decreases. In this case, a controlmodule (not shown) connected to additional detector 3342 as well as to apower amplifier such as power amplifier 2404, 2704, 2904 or 3004 maydeactivate the power amplifier in order to prevent damage thereto.

In the case that the output from the seed laser degrades so as to havean unacceptably narrow line width, non-linear effects will be initiatedin fiber 3344. It is appreciated that fiber 3344 is advantageouslyconfigured so as to be as sensitive as possible to such non-lineareffects. For this purpose, fiber 3344 is preferably of considerablelength and preferably has a small core diameter, in order to increasethe sensitivity of fiber 3344 to the line width of the laser output fromthe seed laser. By way of example only, fiber 3344 may have a length ofapproximately 25 m and a core diameter of approximately 6 microns.

Due to the non-linear effects initiated in fiber 3344 upon narrowing ofthe line width of the output from the seed laser, fiber 3344 preferablybegins to operate as a mirror, reflecting light backwards towardsamplifier 3340. As a result of the reflected light returning toamplifier 3340, an increased signal reaches splitter 3334 and isdetected by detector 3336. Upon detection of an increased signal atdetector 3336, the power amplifier is preferably deactivated in order toprevent damage thereto.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly claimedhereinbelow. Rather, the scope of the invention includes variouscombinations and subcombinations of the features described hereinaboveas well as modifications and variations thereof as would occur topersons skilled in the art upon reading the forgoing description withreference to the drawings and which are not in the prior art.

The invention claimed is:
 1. A laser system comprising: a seed laser; a laser beam splitting and combining subsystem receiving an output from said seed laser and providing a combined laser output having noise; and a noise cancellation subsystem operative to provide a noise cancellation phase correction output based on taking into consideration said noise at intermittent times, and to apply said noise cancellation phase correction output to different sub-beams of said combined laser output at different ones of said intermittent times, said laser beam splitting and combining subsystem additionally varying a phase of said combined laser output during time interstices between said intermittent times to provide spatial modulation of said combined laser output.
 2. A laser system according to claim 1, wherein said spatial modulation of said combined laser output is provided in combination with mechanical spatial modulation of said combined laser output, said spatial modulation in combination with said mechanical spatial modulation being faster than said mechanical spatial modulation in the absence of said spatial modulation.
 3. A laser cutting system comprising a laser system according to claim
 1. 4. A laser additive manufacturing system comprising a laser system according to claim
 1. 5. A laser welding system comprising a laser system according to claim
 1. 6. A free-space optical communication system comprising at least one laser system according to claim
 1. 7. A laser system according to claim 1, and also comprising: a plurality of detectors detecting said combined laser output at said intermittent times during said varying of said phase of said combined laser output, said noise cancellation subsystem being operative to provide said noise cancellation phase correction output based on taking into consideration said noise of said combined laser output, as detected by said plurality of detectors at said intermittent times; and a plurality of optical pathways between said combined laser output and said plurality of detectors for providing therealong said combined laser output to said plurality of detectors, a spatial density of said plurality of optical pathways being greater than a spatial density of said plurality of detectors.
 8. A laser system according to claim 1, said laser beam splitting and combining subsystem splitting said output from said seed laser into a plurality of sub-beams and providing a combined laser output comprising said plurality of sub-beams, said laser system also comprising a phase modulation subsystem grouping at least a portion of ones of said plurality of sub-beams into a multiplicity of groups of sub-beams, said phase modulation subsystem: in parallel across said multiplicity of groups of sub-beams, varying a phase of each sub-beam within each group relative to phases of other sub-beams within said group so as to vary a phase of each group, and varying said phase of each group relative to phases of other ones of said multiplicity of groups, thereby varying a phase of said combined laser output.
 9. A laser system according to claim 8, wherein said phase modulation subsystem comprises an array of mirrors and corresponding focusing lenses for performing said grouping.
 10. A laser system according to claim 8, wherein said phase modulation subsystem comprises a plurality of phase modulators for varying said phases of said sub-beams.
 11. A laser system according to claim 8, and wherein said phase modulation subsystem comprises a multiplicity of detectors corresponding to said multiplicity of groups, for detecting a far field intensity pattern of each of said multiplicity of groups.
 12. A laser system according to claim 11, and also comprising a multiplicity of optical masks masking corresponding ones of said multiplicity of detectors, each optical mask comprising at least one of a transmissive region and a reflective region for respectively providing therethrough and therefrom said far field intensity pattern to said corresponding detector of said multiplicity of detectors.
 13. A laser system according to claim 11, wherein said multiplicity of detectors performs said detecting at least partially mutually simultaneously.
 14. A laser system according to claim 10, and wherein said phase modulation subsystem comprises a multiplicity of additional phase modulators, each additional phase modulator being common to all sub-beams within each said group for varying said phase of each group relative to phases of other ones of said multiplicity of groups.
 15. A laser system according to claim 11, wherein each detector of said multiplicity of detectors comprises a plurality of detectors, said system also comprising a plurality of optical pathways between said far field intensity pattern of each of said multiplicity of groups and each plurality of detectors for providing said far field intensity pattern therealong to said plurality of detectors, a spatial density of said plurality of optical pathways being greater than a spatial density of said plurality of detectors.
 16. A laser system according to claim 8, wherein said varying of said phase of said combined laser output comprises maximizing an intensity of said combined laser output.
 17. A laser system according to claim 8, wherein said varying of said phase of said combined laser output provides spatial modulation of said combined laser output, without involving mechanical spatial modulation of said combined laser output.
 18. A laser system according to claim 8, and wherein said laser beam splitting and combining subsystem provides laser beam amplification downstream of said splitting and upstream of said combining.
 19. A method for performing noise correction on a phase varied laser output comprising: receiving an output from a seed laser; splitting and combining said output to provide a combined laser output having noise; applying a noise cancellation phase correction output to said combined laser output based on taking into consideration said noise at intermittent times, said applying comprising applying said noise cancellation phase correction output to different sub-beams of said combined laser output at different ones of said intermittent times; and additionally varying a phase of said combined laser output during time interstices between said intermittent times, thereby providing spatial modulation of said combined laser output. 